Financial instruments - Financial liabilities at fair value through profit or loss (Details) - GBP (£) £ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Financial liabilities at fair value through profit and loss category
Financial instruments
Carrying Value	£ 93,444	£ 188,813
Fair Value	93,444	188,813
Convertible Senior Secured Notes \| Financial liabilities at fair value through profit and loss category
Financial instruments
Carrying Value	91,271	188,526
Fair Value	91,271	188,526
Convertible Preferred Shares
Financial instruments
Fair Value	1,799
Convertible Preferred Shares \| Financial liabilities at fair value through profit and loss category
Financial instruments
Carrying Value	1,799
Fair Value	1,799
Warrant liabilities \| Financial liabilities at fair value through profit and loss category
Financial instruments
Carrying Value	374	287
Fair Value	£ 374	£ 287

- Definition

The amount of liabilities that are: (a) a contractual obligation: (i) to deliver cash or another financial asset to another entity; or (ii) to exchange financial assets or financial liabilities with another entity under conditions that are potentially unfavourable to the entity; or (b) a contract that will, or may be, settled in the entity’s own equity instruments and is: (i) a non-derivative for which the entity is, or may be, obliged to deliver a variable number of the entity’s own equity instruments; or (ii) a derivative that will, or may be, settled other than by the exchange of a fixed amount of cash or another financial asset for a fixed number of the entity’s own equity instruments. For this purpose, rights, options or warrants to acquire a fixed number of the entity’s own equity instruments for a fixed amount of any currency are equity instruments if the entity offers the rights, options or warrants pro rata to all of its existing owners of the same class of its own non-derivative equity instruments. Also, for those purposes the entity’s own equity instruments do not include puttable financial instruments that are classified as equity instruments in accordance with paragraphs 16A-16B of IAS 32, instruments that impose on the entity an obligation to deliver to another party a pro rata share of the net assets of the entity only on liquidation and are classified as equity instruments in accordance with paragraphs 16C-16D of IAS 32, or instruments that are contracts for the future receipt or delivery of the entity’s own equity instruments. As an exception, an instrument that meets the definition of a financial liability is classified as an equity instrument if it has all the features and meets the conditions in paragraphs 16A-16B or paragraphs 16C-16D of IAS 32. [Refer: Classes of financial instruments [domain]; Financial assets; Derivatives [member]]

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