Statement Of Financial Position [Abstract]
| Concept |
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 2021-03-31 |
As at 2021-03-31 |
As at 2021-03-31 |
As at 2021-03-31 |
As at 2021-03-31 |
As at 2020-03-31 |
As at 2020-03-31 |
As at 2020-03-31 |
As at 2020-03-31 |
As at 2020-03-31 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Statement of financial position [abstract] | |||||||||||||||
| Assets [abstract] | |||||||||||||||
| Non-current assets [abstract] | |||||||||||||||
| Property, plant and equipment | — | — | — |
10,208,400,000
GBP
|
— | — | — |
9,875,200,000
GBP
|
— | — | — | — | — | — | — |
| Right-of-use assets | — | — | — |
129,900,000
GBP
|
— | — | — |
130,800,000
GBP
|
— | — | — | — | — | — | — |
| Goodwill | — | — | — |
91,400,000
GBP
|
— | — | — |
91,400,000
GBP
|
— | — | — | — | — | — | — |
| Intangible assets other than goodwill | — | — | — |
179,600,000
GBP
|
— | — | — |
164,000,000
GBP
|
— | — | — | — | — | — | — |
| Trade and other non-current receivables | — | — | — |
92,100,000
GBP
|
— | — | — |
101,500,000
GBP
|
— | — | — | — | — | — | — |
| Non-current assets | — | — | — |
10,766,600,000
GBP
|
— | — | — |
10,417,100,000
GBP
|
— | — | — | — | — | — | — |
| Current assets [abstract] | |||||||||||||||
| Current inventories | — | — | — |
32,000,000
GBP
|
— | — | — |
30,800,000
GBP
|
— | — | — | — | — | — | — |
| Trade and other current receivables | — | — | — |
606,400,000
GBP
|
— | — | — |
515,200,000
GBP
|
— | — | — | — | — | — | — |
| Cash and cash equivalents | — | — | — |
115,400,000
GBP
|
— | — | — |
56,200,000
GBP
|
— | — | — | — | — | — | — |
| Current assets | — | — | — |
787,600,000
GBP
|
— | — | — |
606,000,000
GBP
|
— | — | — | — | — | — | — |
| Equity and liabilities [abstract] | |||||||||||||||
| Equity [abstract] | |||||||||||||||
| Issued capital | — | — | — |
248,100,000
GBP
|
— | — | — |
237,200,000
GBP
|
— | — | — | — | — | — | — |
| Retained earnings | — | — | — |
473,000,000
GBP
|
— | — | — |
651,700,000
GBP
|
— | — | — | — | — | — | — |
| Share premium | — | — | — |
394,400,000
GBP
|
— | — | — |
148,100,000
GBP
|
— | — | — | — | — | — | — |
| Other reserves | — | — | — |
148,400,000
GBP
|
— | — | — |
101,700,000
GBP
|
— | — | — | — | — | — | — |
| Equity |
248,100,000
GBP
|
394,400,000
GBP
|
473,000,000
GBP
|
1,263,900,000
GBP
|
148,400,000
GBP
|
651,700,000
GBP
|
101,700,000
GBP
|
1,138,700,000
GBP
|
237,200,000
GBP
|
148,100,000
GBP
|
67,900,000
GBP
|
1,243,700,000
GBP
|
137,000,000
GBP
|
236,500,000
GBP
|
802,300,000
GBP
|
| Liabilities [abstract] | |||||||||||||||
| Non-current liabilities [abstract] | |||||||||||||||
| Non-current provisions [abstract] | |||||||||||||||
| Non-current provisions | — | — | — |
21,900,000
GBP
|
— | — | — |
25,200,000
GBP
|
— | — | — | — | — | — | — |
| Trade and other non-current payables | — | — | — |
1,334,000,000
GBP
|
— | — | — |
1,250,300,000
GBP
|
— | — | — | — | — | — | — |
| Deferred tax liabilities | — | — | — |
1,320,600,000
GBP
|
— | — | — |
906,000,000
GBP
|
— | — | — | — | — | — | — |
| Non-current liabilities | — | — | — |
9,231,200,000
GBP
|
— | — | — |
8,806,000,000
GBP
|
— | — | — | — | — | — | — |
| Current liabilities [abstract] | |||||||||||||||
| Current provisions [abstract] | |||||||||||||||
| Current provisions | — | — | — |
38,400,000
GBP
|
— | — | — |
18,000,000
GBP
|
— | — | — | — | — | — | — |
| Trade and other current payables | — | — | — |
655,500,000
GBP
|
— | — | — |
557,100,000
GBP
|
— | — | — | — | — | — | — |
| Current liabilities | — | — | — |
1,059,100,000
GBP
|
— | — | — |
1,078,400,000
GBP
|
— | — | — | — | — | — | — |