Significant accounting policies, estimates and judgements - Currency (Details)	12 Months Ended
Dec. 31, 2023 GBP (£)	Dec. 31, 2023 GBP (£) AUD ($)	Dec. 31, 2023 GBP (£) USD ($)	Dec. 31, 2022 GBP (£)	Dec. 31, 2022 GBP (£) AUD ($)	Dec. 31, 2022 GBP (£) USD ($)	Dec. 31, 2021 GBP (£)	Dec. 31, 2021 GBP (£) AUD ($)	Dec. 31, 2021 GBP (£) USD ($)	Dec. 31, 2023 AUD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 AUD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 AUD ($)	Dec. 31, 2021 USD ($)
Significant accounting policies, estimates and judgements
Annual average exchange rate	0.87	1.63	1.08	0.85	1.52	1.05	0.86	1.57	1.18
Exchange rate	0.87	0.87	0.87	0.89	0.89	0.89	0.84	0.84	0.84	1.63	1.11	1.57	1.07	1.56	1.13

The spot exchange rate at the end of the reporting period. Exchange rate is the ratio of exchange for two currencies. Spot exchange rate is the exchange rate for immediate delivery.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2023-01-01
-Paragraph 112
-Subparagraph c
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2023-en-r&anchor=para_112_c&doctype=Standard
-URIDate 2023-03-23

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Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant