Subclassifications Of Assets, Liabilities And Equities [Abstract]
| Concept |
As at 2023-12-31 |
As at 2022-12-31 |
As at 2021-12-31 |
|---|---|---|---|
| Subclassifications of assets, liabilities and equities [abstract] | |||
| Property, plant and equipment [abstract] | |||
| Property, plant and equipment |
11,800,000
GBP
|
13,500,000
GBP
|
— |
| Intangible assets and goodwill [abstract] | |||
| Intangible assets and goodwill |
25,300,000
GBP
|
25,300,000
GBP
|
— |
| Trade and other non-current receivables [abstract] | |||
| Trade and other non-current receivables |
12,000,000
GBP
|
6,300,000
GBP
|
— |
| Trade and other current receivables [abstract] | |||
| Trade and other current receivables |
52,900,000
GBP
|
55,300,000
GBP
|
— |
| Current prepayments and current accrued income including current contract assets [abstract] | |||
| Current accrued income including current contract assets [abstract] | |||
| Current contract assets |
84,200,000
GBP
|
54,300,000
GBP
|
— |
| Classes of current inventories [abstract] | |||
| Current inventories |
500,000
GBP
|
500,000
GBP
|
— |
| Classes of current inventories, alternative [abstract] | |||
| Cash and cash equivalents [abstract] | |||
| Cash and cash equivalents |
29,300,000
GBP
|
22,500,000
GBP
|
20,300,000
GBP
|
| Current borrowings and current portion of non-current borrowings, by type [abstract] | |||
| Current loans received and current portion of non-current loans received | — | — | — |
| Current secured bank loans received and current portion of non-current secured bank loans received |
10,000,000
GBP
|
15,000,000
GBP
|
— |
| Trade and other non-current payables [abstract] | |||
| Trade and other non-current payables |
3,100,000
GBP
|
2,500,000
GBP
|
— |
| Trade and other current payables [abstract] | |||
| Current accruals and current deferred income including current contract liabilities [abstract] | |||
| Current deferred income including current contract liabilities [abstract] | |||
| Current contract liabilities [abstract] | |||
| Current contract liabilities |
7,200,000
GBP
|
7,700,000
GBP
|
— |
| Trade and other current payables |
126,100,000
GBP
|
96,100,000
GBP
|
— |
| Miscellaneous non-current liabilities [abstract] | |||
| Non-current net defined benefit liability |
11,800,000
GBP
|
12,900,000
GBP
|
— |
| Issued capital [abstract] | |||
| Issued capital |
5,300,000
GBP
|
4,400,000
GBP
|
— |
| Retained earnings [abstract] | |||
| Retained earnings |
34,500,000
GBP
|
29,500,000
GBP
|
— |
| Accumulated other comprehensive income [abstract] | |||
| Revaluation surplus |
–
GBP
|
400,000
GBP
|
— |
| Net assets (liabilities) [abstract] | |||
| Assets |
219,400,000
GBP
|
181,300,000
GBP
|
— |
| Liabilities |
166,000,000
GBP
|
142,600,000
GBP
|
— |
| Assets (liabilities) |
53,400,000
GBP
|
38,700,000
GBP
|
— |
| Net current assets (liabilities) [abstract] | |||
| Current assets |
167,100,000
GBP
|
132,600,000
GBP
|
— |
| Current liabilities |
145,900,000
GBP
|
121,500,000
GBP
|
— |
| Current assets (liabilities) |
21,200,000
GBP
|
11,100,000
GBP
|
— |
| Assets less current liabilities [abstract] |