Statement Of Financial Position [Abstract]
| Concept |
As at 2024-03-31 |
As at 2024-03-31 |
As at 2024-03-31 |
As at 2024-03-31 |
As at 2024-03-31 |
As at 2024-03-31 |
As at 2023-03-31 |
As at 2023-03-31 |
As at 2023-03-31 |
As at 2023-03-31 |
As at 2023-03-31 |
As at 2023-03-31 |
As at 2022-03-31 |
As at 2022-03-31 |
As at 2022-03-31 |
As at 2022-03-31 |
As at 2022-03-31 |
As at 2022-03-31 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Statement of financial position [abstract] | ||||||||||||||||||
| Assets [abstract] | ||||||||||||||||||
| Property, plant and equipment | — | — | — | — | — |
1,436,000,000
GBP
|
1,332,000,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
| Right-of-use assets | — | — | — | — | — |
40,000,000
GBP
|
49,000,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
| Goodwill | — | — | — | — | — |
353,000,000
GBP
|
364,000,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
| Intangible assets other than goodwill | — | — | — | — | — |
301,000,000
GBP
|
287,000,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
| Investments accounted for using equity method | — | — | — | — | — |
71,000,000
GBP
|
75,000,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
| Current tax assets | — | — | — | — | — |
10,000,000
GBP
|
12,000,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
| Deferred tax assets | — | — | — | — | — |
128,000,000
GBP
|
121,000,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
| Cash and cash equivalents | — | — | — | — | — |
542,000,000
GBP
|
650,000,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
| Assets | — | — | — | — | — |
6,336,000,000
GBP
|
7,029,000,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
| Equity and liabilities [abstract] | ||||||||||||||||||
| Equity [abstract] | ||||||||||||||||||
| Issued capital | — | — | — | — | — |
215,000,000
GBP
|
215,000,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
| Retained earnings | — | — | — | — | — |
1,998,000,000
GBP
|
2,077,000,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
| Share premium | — | — | — | — | — |
148,000,000
GBP
|
148,000,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
| Treasury shares | — | — | — | — | — |
17,000,000
GBP
|
19,000,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
| Other reserves | — | — | — | — | — |
36,000,000
GBP
|
118,000,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
| Equity |
36,000,000
GBP
|
1,998,000,000
GBP
|
148,000,000
GBP
|
215,000,000
GBP
|
17,000,000
GBP
|
2,380,000,000
GBP
|
2,539,000,000
GBP
|
148,000,000
GBP
|
215,000,000
GBP
|
19,000,000
GBP
|
2,077,000,000
GBP
|
118,000,000
GBP
|
24,000,000
GBP
|
218,000,000
GBP
|
148,000,000
GBP
|
2,049,000,000
GBP
|
2,441,000,000
GBP
|
50,000,000
GBP
|
| Liabilities [abstract] | ||||||||||||||||||
| Current tax liabilities | — | — | — | — | — |
75,000,000
GBP
|
105,000,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
| Deferred tax liabilities | — | — | — | — | — |
2,000,000
GBP
|
19,000,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
| Liabilities included in disposal groups classified as held for sale | — | — | — | — | — |
35,000,000
GBP
|
25,000,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
| Liabilities | — | — | — | — | — |
3,956,000,000
GBP
|
4,490,000,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |