Statement Of Financial Position [Abstract]
| Concept |
As at 2025-03-31 |
As at 2025-03-31 |
As at 2025-03-31 |
As at 2025-03-31 |
As at 2025-03-31 |
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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Statement of financial position [abstract] | |||||||||||||||
| Assets [abstract] | |||||||||||||||
| Non-current assets [abstract] | |||||||||||||||
| Property, plant and equipment | — | — | — |
13,307,200,000
GBP
|
— | — | — | — | — |
11,766,900,000
GBP
|
— | — | — | — | — |
| Right-of-use assets | — | — | — |
141,000,000
GBP
|
— | — | — | — | — |
143,000,000
GBP
|
— | — | — | — | — |
| Goodwill | — | — | — |
117,300,000
GBP
|
— | — | — | — | — |
112,800,000
GBP
|
— | — | — | — | — |
| Intangible assets other than goodwill | — | — | — |
206,500,000
GBP
|
— | — | — | — | — |
186,500,000
GBP
|
— | — | — | — | — |
| Investments in subsidiaries, joint ventures and associates reported in separate financial statements | — | — | — |
–
GBP
|
— | — | — | — | — |
–
GBP
|
— | — | — | — | — |
| Non-current biological assets | — | — | — |
4,900,000
GBP
|
— | — | — | — | — |
5,700,000
GBP
|
— | — | — | — | — |
| Trade and other non-current receivables | — | — | — |
90,800,000
GBP
|
— | — | — | — | — |
89,200,000
GBP
|
— | — | — | — | — |
| Deferred tax assets | — | — | — |
–
GBP
|
— | — | — | — | — |
–
GBP
|
— | — | — | — | — |
| Non-current assets | — | — | — |
13,934,500,000
GBP
|
— | — | — | — | — |
12,393,100,000
GBP
|
— | — | — | — | — |
| Current assets [abstract] | |||||||||||||||
| Current inventories | — | — | — |
43,200,000
GBP
|
— | — | — | — | — |
40,100,000
GBP
|
— | — | — | — | — |
| Trade and other current receivables | — | — | — |
878,300,000
GBP
|
— | — | — | — | — |
817,300,000
GBP
|
— | — | — | — | — |
| Cash and cash equivalents | — | — | — |
1,048,100,000
GBP
|
— | — | — | — | — |
953,200,000
GBP
|
— | — | — | — | — |
| Current assets | — | — | — |
1,975,200,000
GBP
|
— | — | — | — | — |
1,810,600,000
GBP
|
— | — | — | — | — |
| Equity and liabilities [abstract] | |||||||||||||||
| Equity [abstract] | |||||||||||||||
| Issued capital | — | — | — |
296,300,000
GBP
|
— | — | — | — | — |
295,400,000
GBP
|
— | — | — | — | — |
| Retained earnings | — | — | — |
78,100,000
GBP
|
— | — | — | — | — |
7,900,000
GBP
|
— | — | — | — | — |
| Share premium | — | — | — |
1,378,300,000
GBP
|
— | — | — | — | — |
1,363,100,000
GBP
|
— | — | — | — | — |
| Other reserves | — | — | — |
174,300,000
GBP
|
— | — | — | — | — |
167,600,000
GBP
|
— | — | — | — | — |
| Equity |
296,300,000
GBP
|
174,300,000
GBP
|
78,100,000
GBP
|
1,770,800,000
GBP
|
1,378,300,000
GBP
|
167,600,000
GBP
|
7,900,000
GBP
|
1,363,100,000
GBP
|
295,400,000
GBP
|
1,834,000,000
GBP
|
970,600,000
GBP
|
408,700,000
GBP
|
249,100,000
GBP
|
162,500,000
GBP
|
150,300,000
GBP
|
| Liabilities [abstract] | |||||||||||||||
| Non-current liabilities [abstract] | |||||||||||||||
| Non-current provisions [abstract] | |||||||||||||||
| Non-current provisions | — | — | — |
48,800,000
GBP
|
— | — | — | — | — |
29,600,000
GBP
|
— | — | — | — | — |
| Trade and other non-current payables | — | — | — |
1,839,200,000
GBP
|
— | — | — | — | — |
1,688,500,000
GBP
|
— | — | — | — | — |
| Deferred tax liabilities | — | — | — |
1,472,100,000
GBP
|
— | — | — | — | — |
1,364,500,000
GBP
|
— | — | — | — | — |
| Non-current liabilities | — | — | — |
12,694,000,000
GBP
|
— | — | — | — | — |
11,522,300,000
GBP
|
— | — | — | — | — |
| Current liabilities [abstract] | |||||||||||||||
| Current provisions [abstract] | |||||||||||||||
| Current provisions | — | — | — |
46,400,000
GBP
|
— | — | — | — | — |
53,900,000
GBP
|
— | — | — | — | — |
| Trade and other current payables | — | — | — |
862,200,000
GBP
|
— | — | — | — | — |
724,700,000
GBP
|
— | — | — | — | — |
| Current liabilities | — | — | — |
1,444,900,000
GBP
|
— | — | — | — | — |
847,400,000
GBP
|
— | — | — | — | — |