v3.24.1.1.u2
Pensions and other post-retirement benefits - Schedule of reconciliation of changes in the present value of defined benefit obligations (including unfunded obligations) (Details) - GBP (£)
£ in Millions
12 Months Ended
Mar. 31, 2024
Mar. 31, 2023
Disclosure of operating segments [line items]    
Opening net defined benefit asset £ 1,951 £ 3,075
Changes in net defined benefit liability (asset) [abstract]    
Reclassification to held for sale (note 10) (17) 30
Closing net defined benefit asset 1,814 1,951
UK | Pensions    
Disclosure of operating segments [line items]    
Opening net defined benefit asset 1,614 2,590
Changes in net defined benefit liability (asset) [abstract]    
Reclassification to held for sale (note 10) (17) 30
Closing net defined benefit asset 1,261 1,614
US | Pensions    
Disclosure of operating segments [line items]    
Opening net defined benefit asset 324 484
Changes in net defined benefit liability (asset) [abstract]    
Reclassification to held for sale (note 10) 0 0
Closing net defined benefit asset 408 324
US | Other post-retirement benefits    
Disclosure of operating segments [line items]    
Opening net defined benefit asset 13 1
Changes in net defined benefit liability (asset) [abstract]    
Reclassification to held for sale (note 10) 0 0
Closing net defined benefit asset 145 13
Present value of defined benefit obligation    
Disclosure of operating segments [line items]    
Opening net defined benefit asset (19,226) (23,867)
Changes in net defined benefit liability (asset) [abstract]    
Current service cost (143) (194)
Interest cost (911) (697)
Actuarial (losses)/gains – experience 37 (204)
Actuarial gains/(losses) – demographic assumptions 106 150
Actuarial gains/(losses) – financial assumptions 348 4,428
Past service cost – augmentations and redundancies (9) (8)
Liabilities extinguished on settlements 543 616
Medicare subsidy received (26) (28)
Employee contributions (10) (10)
Benefits paid 1,174 1,290
Exchange adjustments 189 (656)
Reclassification from other post-employment liabilities (11) 0
Reclassification to held for sale (note 10) 72 (46)
Closing net defined benefit asset (17,867) (19,226)
Present value of defined benefit obligation | UK | Pensions    
Disclosure of operating segments [line items]    
Opening net defined benefit asset (10,964) (14,275)
Changes in net defined benefit liability (asset) [abstract]    
Current service cost (45) (69)
Interest cost (536) (334)
Actuarial (losses)/gains – experience (2) (235)
Actuarial gains/(losses) – demographic assumptions 98 135
Actuarial gains/(losses) – financial assumptions 165 3,167
Past service cost – augmentations and redundancies (9) (8)
Liabilities extinguished on settlements 0 0
Medicare subsidy received 0 0
Employee contributions (10) (10)
Benefits paid 710 711
Exchange adjustments 0 0
Reclassification from other post-employment liabilities 0 0
Reclassification to held for sale (note 10) 72 (46)
Closing net defined benefit asset (10,521) (10,964)
Present value of defined benefit obligation | US | Pensions    
Disclosure of operating segments [line items]    
Opening net defined benefit asset (5,736) (6,779)
Changes in net defined benefit liability (asset) [abstract]    
Current service cost (72) (88)
Interest cost (258) (252)
Actuarial (losses)/gains – experience (34) (17)
Actuarial gains/(losses) – demographic assumptions 12 5
Actuarial gains/(losses) – financial assumptions 190 818
Past service cost – augmentations and redundancies 0 0
Liabilities extinguished on settlements 543 616
Medicare subsidy received 0 0
Employee contributions 0 0
Benefits paid 312 426
Exchange adjustments 131 (465)
Reclassification from other post-employment liabilities 0 0
Reclassification to held for sale (note 10) 0 0
Closing net defined benefit asset (4,912) (5,736)
Present value of defined benefit obligation | US | Other post-retirement benefits    
Disclosure of operating segments [line items]    
Opening net defined benefit asset (2,526) (2,813)
Changes in net defined benefit liability (asset) [abstract]    
Current service cost (26) (37)
Interest cost (117) (111)
Actuarial (losses)/gains – experience 73 48
Actuarial gains/(losses) – demographic assumptions (4) 10
Actuarial gains/(losses) – financial assumptions (7) 443
Past service cost – augmentations and redundancies 0 0
Liabilities extinguished on settlements 0 0
Medicare subsidy received (26) (28)
Employee contributions 0 0
Benefits paid 152 153
Exchange adjustments 58 (191)
Reclassification from other post-employment liabilities (11) 0
Reclassification to held for sale (note 10) 0 0
Closing net defined benefit asset £ (2,434) £ (2,526)