Statement Of Financial Position [Abstract]
| Concept |
As at 2023-12-31 |
As at 2023-12-31 |
As at 2023-12-31 |
As at 2023-12-31 |
As at 2023-12-31 |
As at 2023-12-31 |
As at 2023-12-31 |
As at 2022-12-25 |
As at 2022-12-25 |
As at 2022-12-25 |
As at 2022-12-25 |
As at 2022-12-25 |
As at 2022-12-25 |
As at 2022-12-25 |
As at 2021-12-26 |
As at 2021-12-26 |
As at 2021-12-26 |
As at 2021-12-26 |
As at 2021-12-26 |
As at 2021-12-26 |
As at 2021-12-26 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Statement of financial position [abstract] | |||||||||||||||||||||
| Assets [abstract] | |||||||||||||||||||||
| Non-current assets [abstract] | |||||||||||||||||||||
| Property, plant and equipment |
97,600,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
96,500,000
GBP
|
— | — | — | — | — | — | — | — |
| Right-of-use assets |
19,300,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
21,300,000
GBP
|
— | — | — | — | — | — | — | — |
| Investments accounted for using equity method |
25,200,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
25,400,000
GBP
|
— | — | — | — | — | — | — | — |
| Trade and other non-current receivables |
3,700,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
3,400,000
GBP
|
— | — | — | — | — | — | — | — |
| Non-current assets |
377,800,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
373,500,000
GBP
|
— | — | — | — | — | — | — | — |
| Current assets [abstract] | |||||||||||||||||||||
| Current inventories |
11,400,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
11,600,000
GBP
|
— | — | — | — | — | — | — | — |
| Trade and other current receivables |
51,600,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
55,900,000
GBP
|
— | — | — | — | — | — | — | — |
| Cash and cash equivalents |
52,100,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
30,400,000
GBP
|
— | — | — | — |
42,800,000
GBP
|
— | — | — |
| Current assets |
134,700,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
147,200,000
GBP
|
— | — | — | — | — | — | — | — |
| Assets |
512,500,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
520,700,000
GBP
|
— | — | — | — | — | — | — | — |
| Equity and liabilities [abstract] | |||||||||||||||||||||
| Equity [abstract] | |||||||||||||||||||||
| Issued capital |
2,100,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
2,200,000
GBP
|
— | — | — | — | — | — | — | — |
| Retained earnings |
171,100,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
156,600,000
GBP
|
— | — | — | — | — | — | — | — |
| Share premium |
49,600,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
49,600,000
GBP
|
— | — | — | — | — | — | — | — |
| Equity |
134,000,000
GBP
|
171,100,000
GBP
|
500,000
GBP
|
49,600,000
GBP
|
2,100,000
GBP
|
2,600,000
GBP
|
12,500,000
GBP
|
9,000,000
GBP
|
500,000
GBP
|
2,200,000
GBP
|
49,600,000
GBP
|
500,000
GBP
|
112,800,000
GBP
|
156,600,000
GBP
|
2,300,000
GBP
|
105,400,000
GBP
|
1,000,000
GBP
|
58,600,000
GBP
|
49,600,000
GBP
|
4,600,000
GBP
|
500,000
GBP
|
| Liabilities [abstract] | |||||||||||||||||||||
| Non-current liabilities [abstract] | |||||||||||||||||||||
| Non-current provisions [abstract] | |||||||||||||||||||||
| Non-current provisions |
1,800,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
14,300,000
GBP
|
— | — | — | — | — | — | — | — |
| Trade and other non-current payables |
200,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
200,000
GBP
|
— | — | — | — | — | — | — | — |
| Non-current liabilities |
503,100,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
505,000,000
GBP
|
— | — | — | — | — | — | — | — |
| Current liabilities [abstract] | |||||||||||||||||||||
| Current provisions [abstract] | |||||||||||||||||||||
| Current provisions |
2,000,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
1,000,000
GBP
|
— | — | — | — | — | — | — | — |
| Trade and other current payables |
111,400,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
98,600,000
GBP
|
— | — | — | — | — | — | — | — |
| Current liabilities |
143,400,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
128,500,000
GBP
|
— | — | — | — | — | — | — | — |
| Liabilities |
646,500,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
633,500,000
GBP
|
— | — | — | — | — | — | — | — |