v3.26.1
Borrowing facilities - Narrative (Details) - GBP (£)
£ in Millions
Jun. 03, 2026
Mar. 31, 2026
Mar. 31, 2025
Disclosure of detailed information about borrowings [line items]      
Undrawn borrowing facilities   £ 8,007 £ 7,832
In 1 to 2 years      
Disclosure of detailed information about borrowings [line items]      
Undrawn borrowing facilities   5,408 0
In 1 to 2 years | Extension of term of borrowing facilities      
Disclosure of detailed information about borrowings [line items]      
Undrawn borrowing facilities £ 5,158    
Facilities held as backup to commercial paper and similar borrowings      
Disclosure of detailed information about borrowings [line items]      
Undrawn borrowing facilities   7,968 7,792
Facilities available as backup to specific US borrowings      
Disclosure of detailed information about borrowings [line items]      
Undrawn borrowing facilities   £ 39 £ 40