Sensitivities (Tables)

12 Months Ended

Mar. 31, 2024

Disclosure of sensitivity analysis for actuarial assumptions [abstract]

Schedule of sensitivities on areas of estimation uncertainty and on financial instruments

Derivative financial instruments were used to manage foreign currency risk as follows:


	2024					2023
	Sterling £m	Euro £m	Dollar £m	Other £m	Total £m	Sterling £m	Euro £m	Dollar £m	Other £m	Total £m
Cash and cash equivalents	402	—	157	—	559	96	14	53	—	163
Financial investments	1,514	—	2,185	—	3,699	1,031	—	1,574	—	2,605
Borrowings	(14,498)	(11,936)	(18,938)	(1,700)	(47,072)	(14,473)	(11,045)	(15,741)	(1,726)	(42,985)
Pre-derivative position	(12,582)	(11,936)	(16,596)	(1,700)	(42,814)	(13,346)	(11,031)	(14,114)	(1,726)	(40,217)
Derivative effect	(9,102)	12,976	(6,625)	1,958	(793)	(6,751)	10,733	(6,476)	1,738	(756)
Net debt position	(21,684)	1,040	(23,221)	258	(43,607)	(20,097)	(298)	(20,590)	12	(40,973)

The currency exposure on other financial instruments is as follows:


	2024					2023
	Sterling £m	Euro £m	Dollar £m	Other £m	Total £m	Sterling £m	Euro £m	Dollar £m	Other £m	Total £m
Trade and other receivables	280	—	1,878	—	2,158	448	—	1,881	—	2,329
Trade and other payables	(1,330)	—	(2,385)	—	(3,715)	(1,624)	—	(2,629)	—	(4,253)
Other non-current liabilities	(169)	—	(289)	—	(458)	(147)	—	(269)	—	(416)

The table below sets out the sensitivity analysis for certain areas of estimation uncertainty set out in note 1F. These estimates are those that have

a significant risk of resulting in a material adjustment to the carrying values of assets and liabilities in the next year. This includes the impact of

changes in assumptions on the net assets recognised at the balance sheet date and the amount charged to the income statement for the following

year. Note that the sensitivity analysis for the useful economic lives of our gas network assets is included in note 13.


	2024			2023
	Assumptions used	Income statement £m	Net assets £m	Assumptions used	Income statement £m	Net assets £m
Pensions and other post-retirement benefit liabilities (pre-tax):
UK discount rate change¹	1%	22	1,147	1%	29	1,264
US discount rate change¹	1%	18	801	1%	26	977
UK inflation rate change²	1%	8	902	1%	8	933
UK long-term rate of increase in salaries change	1%	4	81	1%	4	50
US long-term rate of increase in salaries change	1%	2	37	1%	4	57
UK change to life expectancy at age 653	one year	2	402	one year	2	441
US change to life expectancy at age 65	one year	2	288	one year	3	344
Assumed US healthcare cost trend rates change	1%	18	276	1%	24	324

US environmental provision4:
Change in the real discount rate	1%	173	173	1%	150	150
Change in estimated future cash flows	20%	462	462	20%	354	354

1.A change in the discount rate is likely to be driven by changes in bond yields and as such would be expected to be offset to a significant degree by a change in the value of the bond

assets held by the plans. In the UK, there would also be a £171 million (2023: £188 million) net assets offset from the buy-in policies, where the accounting value of the buy‑in asset is

set equal to the associated liabilities.

2.The projected impact resulting from a change in RPI reflects the associated effect on escalation rates for pensions in payment and in deferment and future salary increases. The buy‑in

policies would have a £150 million (2023: £164 million) net assets offset to the above.

3.In the UK, the buy-in policies and the longevity swap entered into would have a £126 million (2023: £136 million) net assets offset to the above.

4.In the prior year, our sensitivity analysis included our UK environmental provisions, which are not considered to be a key source of estimation uncertainty in the current year. Accordingly,

comparatives have been restated in line with current year disclosure. As a result of this change, the change in the real discount rate decreased by £9 million and the change in the

estimated future cash flows decreased by £24 million.


	2024			2023
	Assumptions used	Income statement £m	Other equity reserves £m	Assumptions used	Income statement £m	Other equity reserves £m
Financial risk (post tax):
UK inflation change¹	1%	36	—	1%	35	—
UK interest rates change	1%	24	304	1%	34	361
US interest rates change	1%	5	39	1%	14	50
US dollar exchange rate change²	10%	58	268	10%	51	291

1.Excludes sensitivities to LPI curve. Further details on sensitivities are provided in note 32(g).

2.The other equity reserves impact does not reflect the exchange translation in our US subsidiaries’ net assets. It is estimated this would change by £1,680 million (2023: £1,680 million)

in the opposite direction if the dollar exchange rate changed by 10%.

Our commodity contract derivatives are sensitive to price risk. Additional sensitivities in respect to commodity price risk and to our derivative fair

values are as follows:


	2024			2023
	Assumptions used	Income statement £m	Net assets £m	Assumptions used	Income statement £m	Net assets £m
Commodity price risk (post tax):
Increase in commodity prices	10%	43	43	10%	49	49
Decrease in commodity prices	10%	(43)	(43)	10%	(40)	(40)

Assets and liabilities carried at fair value (post tax):
Fair value change in derivative financial instruments¹	10%	(59)	(59)	10%	(60)	(60)
Fair value change in commodity contract derivative liabilities	10%	(6)	(6)	10%	(8)	(8)

1.The effect of a 10% change in fair value assumes no hedge accounting