United States

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 6-K

REPORT OF FOREIGN PRIVATE ISSUER

PURSUANT TO RULE 13a-16 OR 15d-16

OF THE SECURITIES EXCHANGE ACT OF 1934

For the Month of October, 2016

Commission File Number: 001-35892

GW PHARMACEUTICALS PLC

(Translation of registrant’s name into English)

Sovereign House

Vision Park

Histon

Cambridge CB24 9BZ

United Kingdom

(Address of principal executive offices)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1):

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7):

Other Events

On October 19, 2016, GW Pharmaceuticals plc (the “Company”), issued a regulatory news service (“RNS”) announcement stating the Company’s intention to cancel the admission of its 0.1 pence ordinary shares (Ordinary Shares) to trading on AIM on December 5, 2016. The last day of trading on AIM will be December 2, 2016. The Company will retain its U.S. listing on the NASDAQ Global Market of its American Depositary Shares (ADSs) under ticker symbol GWPH. Existing holders of ADSs do not need to take any action as a result of this announcement. The RNS is attached as Exhibit 99.1 hereto and is incorporated by reference herein. In connection with the AIM delisting, the Company’s Chairman delivered a letter to holders of the Company’s Ordinary Shares and the Company published a set of frequently asked questions (FAQs) about the AIM delisting on the investor relations section of its website. The Chairman’s letter and FAQ’s are attached as Exhibit 99.2 and Exhibit 99.3, respectively, and are incorporated by reference herein. The information contained in Exhibit 99.1, Exhibit 99.2 and Exhibit 99.3 hereto shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, unless expressly set forth by specific reference in such a filing.

99.1 Regulatory news service announcement dated October 19, 2016

99.1 Chairman’s Letter to Holders of Ordinary Shares dated October 19, 2016

99.1 AIM Delisting Frequently Asked Questions published October 19, 2016

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

Exhibit 99.1

GW Pharmaceuticals plc Announces Intention to Continue Trading Exclusively on NASDAQ and Planned Cancellation of Trading of Ordinary Shares on AIM

GW remains headquartered in UK and continues to expand UK operations

London, UK, October 19 2016: GW Pharmaceuticals plc (Nasdaq: GWPH, AIM: GWP, “GW” or “the Company”), a biopharmaceutical company focused on discovering, developing and commercializing novel therapeutics from its proprietary cannabinoid product platform, today announced the Company’s intention to cancel the admission of its 0.1 pence ordinary shares (Ordinary Shares) to trading on AIM on 5 December, 2016. The last day of trading on AIM will be 2 December, 2016. GW will retain its U.S. listing on the NASDAQ Stock Exchange of American Depositary Receipts (ADRs) under ticker symbol GWPH. Existing holders of ADRs do not need to take any action as a result of this announcement.

“Since listing on NASDAQ in 2013, GW has raised nearly $800 million largely from U.S. investors which has helped transform our business and its prospects. With the vast majority of shares now held and traded in the U.S. in the form of ADRs, the time is right to reduce the complexity and expense of a dual listing,” stated Justin Gover, GW’s Chief Executive Officer. “The proposed cancellation of the AIM listing has no impact on GW’s UK presence, which has significantly increased in recent years. We remain firmly committed to bringing important products to the global market, products that are both researched and manufactured in the UK.”

At the date of this announcement, 78 percent of GW’s Ordinary Shares are held in ADR form and tradeable on the NASDAQ market with approximately 94 percent of trading in the last six months taking place on the NASDAQ market. All shareholders who have not already converted their Ordinary Shares into ADRs are able to do so at any time. Following cancellation of the AIM listing, shares will only be tradeable on the NASDAQ market in the United States.

Following the cancellation of the AIM listing, GW will continue to be headquartered and domiciled in the UK, will continue to comply fully with the requirements of the Companies Act, will be subject to the UK Takeover Code, and will be subject to UK corporation tax. GW currently has 420 employees in the UK and expects this number to continue to increase as it prepares for global regulatory submissions and approvals of Epidiolex, its investigational product for the treatment of a number of rare childhood-onset epilepsy disorders, as well as advance its cannabinoid product pipeline.

Background

Having been listed on the AIM market of the London Stock exchange since 2001, GW completed a successful Initial Public Offering (IPO) on the NASDAQ Global exchange in May 2013, with the result that a dual-listing was achieved. The liquidity of trading of GW’s shares was immediately enhanced by the NASDAQ listing and demand from U.S. investors following material corporate progress has led to share price growth and rapid increase in the proportion of GW’s shares that are held through NASDAQ.

GW believes that this trend is likely to continue, leading to a further reduction in the proportion of shares held and traded through AIM. The Company expects that continuation of the decline in proportion of shares held and traded through AIM is likely to lead to a decrease in the liquidity of AIM trading and that it would be advantageous for all GW shareholders to combine trading volumes from both markets onto a single exchange in one time zone.

Prior to making the decision to cancel admission of the Company’s shares to trading on AIM, the Directors considered whether it would be appropriate to seek to transfer the admission of the Ordinary Shares from AIM to the Official List of the UK Listing Authority and to trading on the London Stock Exchange’s main market for listed securities. Having carefully considered this option the Board believes that the existing NASDAQ listing provides sufficient access to investment in GW by investors in the UK, US and further afield and that a main market listing would not be advantageous at this time.

The AIM Rules require that unless the London Stock Exchange otherwise agrees a cancellation of a company’s shares from trading on AIM requires the consent of votes cast by the company’s shareholders at a general meeting. In this instance, given the Company’s listing of the ADRs on NASDAQ enables Shareholders to trade their shares in the Company, the London Stock Exchange has agreed that shareholder consent in a general meeting is not required to complete the AIM Delisting. An explanatory circular will be sent to Shareholders in due course which will be made available on the Company’s website in accordance with the AIM Rules.

Share Conversion

GW’s Ordinary Shares will continue to be traded on the AIM market until close of business on 2nd December 2016. Thereafter, shareholders can choose to maintain ownership of their Ordinary Shares but these Ordinary Shares will not be tradeable on NASDAQ in this form. In order to sell Ordinary Shares following the cancellation of the AIM listing selling shareholders will need to convert their Ordinary Shares into GW’s ADRs. Each ADR represents twelve Ordinary Shares. This conversion can be made at any time, including before the cancellation of the AIM listing. GW advises holders of Ordinary Shares to seek independent financial advice regarding the cancellation of the AIM listing and the conversion of their Ordinary Shares into ADRs. Full details of the process to be followed to convert Ordinary Shares into ADRs, the forms to be completed and contacts at GW’s Depositary bank, Citibank, are included on GW’s website in the Investor Relations section.

We will be writing to all shareholders on the GW Ordinary share register today enclosing instructions and forms to be completed by brokers and by individual shareholders to convert their Ordinary shares into ADRs.

Contacts for questions:

Questions from individual shareholders should be addressed to the Shareholder services helpline operated by GW’s registrars, Capita, on 0371 664 0321.

Brokers seeking further information should contact our Depositary bank, Citibank, by email at dcc.adr@citi.com

Further information can be found within the investors section of the GW website at: ir.gwpharm.com

About GW Pharmaceuticals plc

Founded in 1998, GW is a biopharmaceutical company focused on discovering, developing and commercializing novel therapeutics from its proprietary cannabinoid product platform in a broad range of disease areas. GW commercialized the world’s first plant-derived cannabinoid prescription drug, Sativex®, which is approved for the treatment of spasticity due to multiple sclerosis in 28 countries outside the United States. GW is advancing an orphan drug program in the field of epilepsy with a focus on Epidiolex® (cannabidiol), which is in Phase 3 clinical development for the treatment of Dravet syndrome, Lennox-Gastaut syndrome, Tuberous Sclerosis Complex and expects to commence a Phase 3 program in Infantile Spasms. GW has a deep pipeline of additional cannabinoid product candidates which includes compounds in Phase 1 and 2 trials for glioma, schizophrenia and epilepsy. For further information, please visit www.gwpharm.com.

Forward-looking statements

This news release contains forward-looking statements that reflect GW's current expectations regarding future events, Actual events could differ materially from those projected herein and depend on a number of factors, including (inter alia), the success of GW’s research strategies, the applicability of the discoveries made therein, the successful and timely completion of uncertainties related to the regulatory process, and the acceptance of Sativex, Epidiolex and other products by consumer and medical professionals. A further list and description of risks and uncertainties associated with an investment in GW can be found in GW’s filings with the U.S. Securities and Exchange Commission. Existing and prospective investors are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date hereof. GW undertakes no obligation to update or revise the information contained in this press release, whether as a result of new information, future events or circumstances or otherwise.

Enquiries:

Exhibit 99.2

GW PHARMACEUTICALS PLC

(Incorporated and registered in England and Wales

under the Companies Acts 1985 and 2006 with registered number 04160917)

Cancellation of the admission to trading on the Alternative Investment Market (“AIM’) of the Ordinary Shares

The distribution of this document in jurisdictions other than the United Kingdom may be restricted by law and, therefore, persons into whose possession this document comes should inform themselves about and observe any such restrictions. Any failure to comply with these restrictions may constitute a violation of the securities laws of any such jurisdiction.

This document contains forward-looking statements, including, without limitation, statements containing the words “targets”, “believes”, “expects”, “estimates”, “intends”, “may”, “plan”, “will”, “anticipates”” and similar expressions (including the negative of those expressions). The Directors believe that the expectations reflected in these statements are reasonable but forward-looking statements involve unknown risks, uncertainties and other factors which may cause the actual results, financial condition, performance or achievements of the Company, or industry results, to be materially different from any future results, performance or achievements expressed or implied by those forward-looking statements. Given these uncertainties, shareholders are cautioned not to place any undue reliance on those forward-looking statements. The forward-looking statements contained in this document are made on the date of this document, and the Company and the Directors are not under any obligation to update those forward-looking statements in this document to reflect actual future events or developments.

EXPECTED TIMETABLE

Each of the dates and times in the above timetable is subject to change without further notice.

All of the times referred to in this document refer to London time.

LETTER FROM THE CHAIRMAN

GW PHARMACEUTICALS PLC

(Incorporated and registered in England and Wales

under the Companies Acts 1985 and 2006 with registered number 04160917)

19 October 2016

Dear Shareholder

CANCELLATION OF THE ADMISSION TO TRADING ON AIM OF THE ORDINARY SHARES

On 19 October 2016, it was announced that the Board of Directors of the Company had resolved to cancel the admission of Ordinary Shares to trading on AIM (“AIM Delisting”). Following AIM Delisting, the Company’s American Depositary Receipts (“ADRs”) will remain listed on NASDAQ and all public trading of shares in the Company will take place on that exchange.

The purpose of this letter is to provide you with the background to and reasons for the AIM Delisting, and to explain why the Directors consider AIM Delisting to be in the best interests of the Company and its shareholders as a whole.

The AIM Delisting will take effect on 5 December 2016 and the last day of trading on AIM will be 2 December 2016. By providing Shareholders with substantial advance notice, together with clear guidance as to how to convert Ordinary Shares into the Company’s ADRs listed on NASDAQ, it is expected that Shareholders who wish to convert their Ordinary Shares into ADRs tradeable on NASDAQ will be able to do so with relative ease.

The Company’s Ordinary Shares were admitted to trading on AIM in 2001. AIM provided GW with important access to capital and share trading liquidity during the formative phase of its business, enabling the Company to invest in and develop the cannabinoid technology platform upon which its pipeline of future medicines relies. In May 2013, the Company completed a successful initial public offering (or IPO) of ADRs on NASDAQ, with the result that dual-listed status was achieved. The liquidity of trading of GW’s Ordinary Shares was immediately enhanced by the NASDAQ listing and demand from US investors has led to a rapid increase in the proportion of GW’s Ordinary Shares that are held as ADRs and traded via NASDAQ. At the date of this letter 78% of Ordinary Shares are held in ADR form and over 94% of shares traded in the last six months were traded in the form of ADRs on NASDAQ.

The Directors believe that if the Ordinary Shares were to continue to be admitted to trading on AIM the trend towards the holding of Ordinary Shares in ADR form and growth in the proportion of trading in ADR form on NASDAQ would continue, leading to a further reduction in the proportion of Ordinary Shares traded on AIM. The Directors believe that a continuation of the decline in the proportion of shares traded on AIM would be likely to lead to a decrease in the liquidity of AIM trading and that it would therefore be advantageous for all Shareholders to combine trading volumes from both markets onto a single exchange.

The Directors further believe that the AIM Delisting will:

Accordingly, the Directors believe that it is no longer in the best interests of the Company or its Shareholders as a whole for the Company to retain its AIM quotation.

Prior to making the decision to cancel admission of the Company’s shares to trading on AIM, the Directors considered whether it would be appropriate to seek to transfer the admission of the Ordinary Shares from AIM to the Official List of the UK Listing Authority and to trading on the London Stock Exchange’s main market for listed securities. Having carefully considered this option the Board believes that the existing NASDAQ listing provides sufficient access to investment in GW by investors in the UK, US and further afield and that a main market listing would not be advantageous at this time.

The AIM Rules require that, unless the London Stock Exchange otherwise agrees, cancellation of an AIM company’s admission of its securities to trading on AIM must be conditional upon the consent of not less than 75 percent of votes cast by its Shareholders, given at a general meeting. In the case of the Company, given that the listing of the ADRs on NASDAQ enables Shareholders to trade their shares in the Company, the London Stock Exchange has agreed that shareholder consent in a general meeting is not required to complete the AIM Delisting.

Ordinary Shares will continue to be traded on AIM until close of business on 2 December 2016. AIM Delisting will take effect at 7.00 a.m. on 5 December 2016. Thereafter, Ordinary Shares will continue to be capable of being held and transferred in certificated form but there will be no public market in the UK on which Shareholders will be able to trade Ordinary Shares. However, the NASDAQ listing of ADRs will not be affected by AIM Delisting and Shareholders will be able to trade their shares in the Company on NASDAQ by converting them to ADRs.

The process of converting Ordinary Shares into ADRs is straightforward. An explanation of the key steps in the conversion process and contact details are provided in the appendices attached to this letter.

Shareholders should consider converting their Ordinary Shares into ADRs prior to AIM Delisting for the following reasons:

Shareholders holding Ordinary Shares not in ADR form are recommended to consult their stockbroker, bank manager, solicitor, accountant or other independent financial adviser authorised under the Financial Services and Markets Act 2000, as amended, or equivalent adviser outside the United Kingdom, in relation to the action they should take in relation to their Ordinary Shares.

GW Pharmaceuticals plc intends to continue to be a UK tax resident company managed from the UK and, accordingly, will pay UK corporation tax on future profits derived from UK-based research and development and UK-based manufacturing operations. Although the most rapidly growing part of our business is currently our US-based commercial team, the Directors expect that for the foreseeable future the majority of GW’s employees, much of the Group’s R&D activities, all of the Group’s intellectual property and all of the Group’s manufacturing operations will remain in the UK. The impact of the proposed AIM Delisting on the day-to-day operation of the business of the Group is expected to be minimal.

As a company incorporated in England and Wales, GW Pharmaceuticals plc will continue to be subject to the requirements of the Companies Act 2006. For so long as the UK Panel on Takeovers and Mergers determines that the Company has its place of central management and control in the United Kingdom, the Company will continue to be subject to the UK City Code on Takeovers and Mergers.

Following the AIM Delisting, the Company will no longer be subject to the AIM Rules for Companies. However, the Company will continue to comply with all regulatory requirements for the NASDAQ listing of its ADRs, including all applicable rules and regulations of the US Securities and Exchange Commission.

Many investors purchase AIM-quoted shares because they are classed as unlisted/unquoted securities which may qualify for relief from inheritance taxation and certain other preferential tax benefits. GW cannot and does not provide any form of taxation advice to Shareholders and therefore Shareholders are strongly advised to seek their own taxation advice to confirm the consequences for them of continuing to hold GW’s unlisted Ordinary Shares or converting Ordinary Shares into ADR form.

Based on historic correspondence with HMRC, the Company’s understanding is as follows (but it should be noted that the Company has not taken steps to confirm the current position with HMRC and therefore the following should not be relied upon by Shareholders without taking further advice):

GW’s Board of Directors and I believe that cancellation of the admission to trading on AIM of GW Pharmaceuticals plc’s shares is an appropriate next step for the Company and is in the best interests of Shareholders as a whole. Further information about the process required to convert Ordinary Shares into ADRs tradeable on NASDAQ, together with a set of Frequently Asked Questions can be found on the following pages of appendices to this letter.

Should you require further information or assistance, further information can be found within the Investor Relations section of the GW website at www.gwpharm.com and a Shareholder assistance advice line is being operated by the Company’s registrar, Capita Asset Services, which can be accessed by all Shareholders on 0371 664 0321*

Yours sincerely

Dr Geoffrey Guy

Chairman

Definitions

In this document, the following words and expressions shall, except where the context requires otherwise, have the following meanings:

APPENDIX A

My GW Ordinary Shares are held by my broker in CREST.

What do I need to do to convert my Ordinary shares into GW’s ADRs tradable on NASDAQ?

To initiate the conversion process, your broker or delivering agent should be instructed to complete the attached form and send to Citibank London directly at the following email address dcc.adr@citi.com

Questions from brokers about this process should be addressed by email to: dcc.adr@citi.com

Once the Ordinary Shares have been received into Citibank London’s CREST account (BA01D), Citibank London will then confirm receipt of the shares by notifying our Depositary, Citibank in New York.

Citibank New York will in turn arrange to issue the corresponding number of ADRs to your broker’s Depository Trust Company (“DTC”) Participant account.

Important Notes for completion of the attached form:

Form to be completed by broker and sent to Citibank:

Citibank London as Custodian requires this page to be either faxed to: +353 1 622 0999, or e-mailed as a PDF file, in a secured format to dcc.adr@citi.com

In the email subject field, please state: UK ADR CREATION – SDRT CERTIFICATION.

Any questions should be directed to dcc.adr@citi.com

Please ensure that faxes or emails are sent in as early as possible to ensure settlement.

Indemnity:

“We shall indemnify and hold Citibank, N.A. (“the Bank”) harmless against all claims, losses, damages, costs and expenses (including reasonable legal fees and disbursements), penalties and taxes (including any interest and penalties for late payment of tax) incurred by the Bank or to which the Bank may become subject to and arising directly from the deposit of the above securities with the Bank or the failure by any person to pay (or discharge) any stamp duty, stamp duty reserve tax, or any other similar duty or tax in connection with the above securities deposited with the Bank. If and to the extent that the deposit of the securities results from the exercise of an option or options, we hereby represent and warrant that the arrangements in respect of the option or options pursuant to the exercise of which the securities are delivered, including the timing of grant and exercise, and the premium/strike ratio, are bona fide and commercial, and are not motivated primarily by or for the avoidance of UK stamp duty reserve tax.”

SDRT Note: It is required that the Broker allege in CREST GUI a declaration of SDRT at 1.5%, include the stamp status, and Stampable Consideration. If the ISIN is flagged as Stamp exempt by CREST at the time of transfer that will supersede the SDRT value input by the broker.

Delisting from AIM and proposed transfer of Ordinary Shares into American Depository Receipts listed on NASDAQ

TRANSFER FORM –

for Shareholders who hold their GW Ordinary Shares in certificated form

and who wish to transfer them into ADRs listed on NASDAQ

IF YOU DO NOT WISH TO TRANSFER YOUR ORDINARY SHARES INTO AMERICAN DEPOSITARY RECEIPTS,

DO NOT COMPLETE AND RETURN THIS TRANSFER FORM

APPENDIX B – TRANSFER FORM

APPENDIX B - TRANSFER FORM

TRANSFER FORM INSTRUCTIONS AND FURTHER NOTES

ARE SET OUT ON PAGES 5 AND 6

PLEASE COMPLETE THIS FORM USING BLACK INK ONLY

APPENDIX B - TRANSFER FORM

APPENDIX B - TRANSFER FORM

HOW TO COMPLETE THIS FORM

APPENDIX B – TRANSFER FORM

NOTES REGARDING THE COMPLETION AND LODGING OF THIS TRANSFER FORM

All signatures by individual Shareholders or their solicitors must be independently witnessed and each witness must complete his or her details and sign his or her name in the place provided in Box 4A of this Transfer Form next to the signature of the relevant Shareholder (or his or her solicitor as the case may be). A company may either execute under seal, the seal being affixed and witnessed in accordance with its articles of association or other regulations, or, if applicable, in accordance with section 44 of the Companies Act 2006 in Box 4B.

If you do not wish to participate in this Transfer Offer, you should not complete and return this Transfer Form. The following suggestions are made to avoid delay and inconvenience.

Send this Transfer Form by the quickest means (such as air mail) to the holder for execution but do not send it into any of the Restricted Jurisdictions. If he/she has executed a relevant power of attorney, have this Transfer Form signed by the attorney. In the latter case, the original power of attorney (or a duly certified copy thereof, as provided in the Powers of Attorney Act 1971) must be lodged with this Transfer Form for noting. No other signatures will be accepted.

If probate or letters of administration has/have been registered with the Company (or with the Company’s registrar, Capita Asset Services, The Registry, 34 Beckenham Road, Beckenham, Kent BR3 4TU) this Transfer Form must be executed by the personal representative(s) of the deceased each in the presence of a witness. If probate or letters of administration has/have been granted but have not been registered with the Company (or with the Company’s registrar, Capita Asset Services, The Registry, 34 Beckenham Road, Beckenham, Kent BR3 4TU), the personal representative(s) should execute this Transfer Form and forward it to Capita Asset Services at the address shown on page 2, together with the share certificate(s) and/or other document(s) of title. A copy of the probate or letters of administration should accompany the Transfer Form or be lodged as soon as possible thereafter and, in any event, so as to reach Capita Asset Services at the address shown on page 2 no later than 1.00 p.m. on 15 November 2016.

This Transfer Form is valid if executed by all the surviving holders and lodged with Capita Asset Services with share certificate(s) and/or other document(s) of title at the address shown on page 2, accompanied by the death certificate, probate or letters of administration of the deceased holder.

If your share certificate(s) and/or document(s) of title is/are held by your stockbroker, bank or other agent, complete this Transfer Form and, if the share certificate(s) and/or other document(s) of title is/are readily available, deliver this completed Transfer Form to your agent for lodging with Capita Asset Services at the address shown on page 2 accompanied by the relevant share certificate(s) and/or document(s) of title.

If your share certificate(s) and or document(s) of title is/are not readily available, you should complete this Transfer Form and lodge it, together with a note of explanation and arrange for the share certificate(s) and/or document(s) of title to be forwarded as soon as possible thereafter and, in any event, so as to arrive by no later than 1.00 p.m. on 15 November 2016. No acceptances of the Block Transfer process will be accepted unless share certificate(s) and/or other document(s) of title or an acceptable indemnity in lieu thereof is/are received by Capita Asset Services at the address shown on page 2 no later than 1.00 p.m. on 15 November 2016.

Complete and send this Transfer Form duly completed and signed in the reply-paid envelope or by hand (during normal business hours only), with a letter of explanation and any share certificate(s) available, to Capita Asset Services at the address shown on page 2. At the same time, you should request a letter of indemnity from the Company’s registrar, Capita Asset Services, The Registry, 34 Beckenham Road, Beckenham, Kent BR3 4TU, which should be completed in accordance with the instructions given. When completed, the letter of indemnity must be lodged with Capita Asset Services at the address shown on page 2 by not later than 1.00 p.m. on 15 November 2016. Indemnities will only be accepted at the discretion of GW pharmaceuticals plc. No acceptances of the Transfer Offer will be accepted unless share certificate(s) and/or other document(s) of title or an acceptable indemnity in lieu thereof is/are received by Capita Asset Services at the address shown on page 2 no later than 1.00 p.m. on 15 November 2016.

You should take the action set out an Appendix A of the Chairman’s letter to arrange for your stockbroker to transfer your Ordinary shares into American Depository Receipts via our depositary bank, Citibank. You should not complete a Transfer Form in respect of any Ordinary Shares held in CREST.

If you are a CREST sponsored member, you should refer to your CREST sponsor as only your CREST sponsor (i.e. broker) will be able to act on your behalf with Citibank, by sending the necessary Appendix A form in the Chairman’s Letter.

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Exhibit 99.3

AIM DELISTING – FREQUENTLY ASKED QUESTIONS:

I already hold GW’s American Depositary Receipts “ADRs” – Am I affected by the AIM Delisting?

GW’s NASDAQ listed ADRs will continue to trade as normal. In theory, AIM Delisting should lead to enhanced liquidity on the NASDAQ market as all trading volume will be transacted via NASDAQ. Existing holders of GW’s NASDAQ listed ADRs do not need to take any action in response to this letter.

How does the price of GW’s NASDAQ listed ADRs compare to the AIM Ordinary share price?

GW Pharmaceuticals currently maintains a listing of its ADR on the NASDAQ Stock Market. An ADR is a financial instrument that represents twelve of GW’s Ordinary Shares. The price of an ADR is expressed in US dollars, and is linked to the value of the twelve Ordinary Shares that it represents. In practice, as 94% of trading in GW’s Ordinary Shares occurs through ADRs on NASDAQ, the share price tends to be driven by supply and demand on the NASDAQ market. The AIM share tends to track the NASDAQ ADR price very closely.

At any time the price of our Ordinary Shares and our NASDAQ listed ADRs can be compared by dividing the ADR price by twelve and then dividing by the current US dollar exchange rate to calculate the equivalent sterling denominated price per Ordinary Share.

As illustrated below, the price of an ADR (converted into a sterling price per ordinary share equivalent) and an AIM quoted Ordinary Share have historically tracked each other very closely:

Illustration of relationship between ADR price and AIM Ordinary Share price

Once you have converted your ordinary shares into ADRs, your investment will be US dollar denominated. This means that when valued in pounds sterling, its value will fluctuate on a day-to-day basis in line with movements in £:$ exchange rate. In fact, this already happens with the AIM share price.

Once the AIM Delisting takes effect, there will no longer be a published price for an individual Ordinary Share. It will, however, always be possible to calculate the value of an individual Ordinary Share in sterling by taking the NASDAQ ADR market price, dividing by twelve and dividing by the dollar to sterling exchange rate.

Also, after Delisting, the price of a single GW Ordinary Share price will no longer be published in UK newspapers or online. However, the NASDAQ share price is always available via GW’s website at www.gwpharm.com or otherwise, can be easily found online through a broad range of financial websites.

Do I need to sell my AIM quoted Ordinary Shares or must I convert them into GW’s NASDAQ listed ADRs?

Shareholders who own GW’s Ordinary Shares now have three options:

The process for converting your Ordinary Shares is set out in the following pages. If your investment is currently managed by a broker, your broker will be able to manage the conversion process for you in accordance with the process set out on Appendix A.

Those Shareholders who own shares in certificated form can also convert to ADRs by following the process set out in the attached Appendix B.

GW’s Ordinary shares will continue to be a valid equity interest in GW Pharmaceuticals plc with full retained voting rights, rights to future dividends, etc. The only change is that the shares will no longer be publicly tradeable on AIM.

Can I continue to hold GW’s Ordinary Shares after the AIM Delisting?

Should you wish to do so, it will be possible to continue to hold GW’s Ordinary Shares after the AIM Delisting. However, these shares will be illiquid and untradeable on a public market. A public sale will require you to go through the conversion process into ADRs via our depositary bank, and any future sale will need to be via a broker with US share trading capability. Note that conversion into ADRs after the AIM Delisting may incur UK stamp duty or stamp duty reserve tax (currently 1.5% of the market value of the shares converted) and fees of up to 5 cents per ADR may be levied by Citibank upon conversion.

The timescale for conversion of an Ordinary Share via a broker into ADR form should typically take 4-5 days, although the timescale will be dependent upon prompt action by your broker.

How do I buy and sell GW’s NASDAQ listed ADRs?

The majority of brokers have the capability to hold US exchange-listed securities and are capable of buying and selling them for you. There is a small annual holding cost, currently US $0.02 per ADR per annum levied by our depositary bank1 (currently equating to less than 0.1% of the value of each ADR), and brokers may also charge a small annual fee for holding a US security on your behalf.

Should you wish to add to your holding, you should be able to purchase further ADRs via your broker. You will simply need to instruct your broker to purchase GWPH ADRs (NASDAQ Ticker: GWPH).

If you wish to continue to hold your investment directly, without engaging the services of a broker, there is a scheme operated by Computershare (our depositary bank’s transfer agent and registrar) whereby your ADRs will be held electronically on the register by Computershare on your behalf. See further details attached on Appendix B.

Will AIM Delisting affect my rights as a Shareholder?

As a company incorporated in England and Wales, GW Pharmaceuticals plc will continue to be subject to the requirements of the Companies Act 2006. For so long as the UK Panel on Takeovers and Mergers determines that the Company has its place of central management and control in the United Kingdom, the Company will continue to be subject to the UK City Code on Takeovers and Mergers.

Following the AIM Delisting, the Company will no longer be subject to the AIM Rules for Companies. However, the Company will continue to comply with all regulatory requirements for the NASDAQ listing of its ADRs, including all applicable rules and regulations of the US Securities and Exchange Commission.

Shareholders who continue to hold Ordinary shares will continue to be notified in writing of the availability of key documents on our website, including publication of Annual Reports and Annual General Meeting documentation. ADR holders will be able to access all such information via the GW website.

Ordinary shareholders and ADR holders will both be eligible to receive future dividends.

I currently hold my Ordinary Shares in the form of a paper certificate– how does this affect me?

For those shareholders, who currently hold their shares in paper certificated form, AIM Delisting will have little immediate effect. Shares in paper certificate form are not currently immediately tradeable as in order to sell them they need to be deposited with a broker and “dematerialised” so that they are held in electronic form in CREST. Only when they have been converted into electronic form by a broker can they then be traded.

If you choose to retain your Ordinary Shares in certificated form you will need to follow a very similar process in future in order to convert into ADR form via a broker when you wish to sell them. The key difference is that your broker would need to contact GW’s depositary bank (Citibank, via the process set out on Appendix A to this letter) in order for your Ordinary Shares to be converted into ADRs and credited to the account held by your broker. Upon receiving instructions to do so, your broker would then sell your ADRs via NASDAQ and would remit the proceeds to your personal account.

I want to convert to ADRs but do not want to engage a broker at this time – how do I do this?

Should you wish to retain a direct investment in GW, without retaining the services of a broker to hold your investment, you can elect to deal direct with Citibank to convert your Ordinary Shares to ADRs. These will then be held in Direct Registered Shares (“DRS”) form, in your name via a facility operated by Computershare on behalf of Citibank. You will then be able to initiate sales or further ADR purchases by directly contacting Computershare.

See Appendix B attached to this letter for further details.

My broker currently holds my GW Ordinary Shares within a CREST nominee account – how will this affect my shareholding?

Most UK brokers have the capability of holding and trading NASDAQ-listed securities. Hence, in order that you continue to hold a readily tradeable form of security you should contact your broker and request that your broker converts your GW Ordinary Shares into ADRs by following the process set out on Appendix A to this letter. Essentially your broker will contact Citibank (GW’s depositary bank), to provide certain details by email and will then transmit your Ordinary Shares electronically to Citibank’s CREST account.

Is there a cost to convert and hold my GW investment in the form of ADRs?

There will be no cost of converting GW Ordinary Shares to ADRs, prior to the date of AIM Delisting. Thereafter, conversion fees may be charged at the discretion of Citibank.

An annual holding fee, currently US $0.02 per ADR², is levied by the depositary bank in August. This is typically paid and charged to your account by your by your broker on an annual basis.

How will this affect the tax treatment of GW’s AIM quoted Ordinary Shares?

GW cannot and does not provide any form of taxation advice to Shareholders and therefore Shareholders are strongly advised to seek their own taxation advice to confirm the consequences for them of continuing to hold GW’s unlisted Ordinary Shares or converting Ordinary Shares admitted to AIM into ADR form.

Based on historic correspondence with HMRC, the Company’s understanding is as follows (but it should be noted that the Company has not taken steps to confirm the current position with HMRC and therefore the following should not be relied upon by Shareholders without taking further advice):

I originally invested under the Enterprise Investment Scheme “EIS” scheme – how does this affect the EIS qualifying status of my investment?

As above, Shareholders should seek their own taxation advice. However, the Company’s understanding (again, based on historic correspondence with HMRC) is that conversion from Ordinary Shares to ADRs should not as a general matter be classified as a disposal event for UK tax purposes and listing ADRs on NASDAQ or the AIM Delisting are not of themselves likely to affect the EIS position of current Shareholders.

I currently hold my shares in an ISA – can I continue to do so?

Although the AIM Delisting does not directly impact on the ability of a UK shareholder to retain their holding of Ordinary Shares, we understand that some UK ISA operators, particularly those that involve an on-line share trading account, insist that the shares held in the ISA must be publicly quoted and may only allow trading in UK companies via low cost on-line trading facilities.

Please ask your ISA provider to confirm whether they will allow you to continue to hold your GW Ordinary Shares or whether they are able to convert and hold GW’s NASDAQ listed ADRs on your behalf.

I currently hold my shares in a self-Invested personal pension “SIPP” – can I continue to do so?

Although the AIM Delisting does not impact on the ability of a UK shareholder to retain their holding of Ordinary Shares, we understand that some SIPP scheme administrators, particularly those that involve an online share trading account, insist that the shares held in an individual’s SIPP must be publicly quoted and sometimes only allow trading in UK companies on-line. Please ask your SIPP provider to confirm whether they will allow you to continue to hold your GW Ordinary Shares or whether they are able to convert your shareholding into ADRs and continue to hold GW’s ADRs on your behalf.

I have further questions that are not dealt with sufficiently here – where can I find further information?

I have lost my original Ordinary Share certificate – how do I get another one in order to progress conversion to ADRs: