Ordinary shares (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2024 Vote £ / shares $ / shares shares	Dec. 31, 2023 £ / shares $ / shares shares
Ordinary shares
Vote per ordinary share | Vote	1
Dividends declared | $ / shares	$ 0	$ 0
Ordinary shares, shares authorized | shares	61,876,165	59,612,613
Ordinary shares, nominal value | £ / shares	$ 0.01	$ 0.01