| Summary of Significant Accounting Policies - Options (Details) - £ / shares | 3 Months Ended | |||
|---|---|---|---|---|
| Mar. 25, 2025 | Mar. 20, 2025 | Dec. 31, 2024 | Dec. 31, 2023 | |
| Nominal value of ordinary shares | £ 0.001 | £ 0.001 | £ 0.001 | |
| Exercise price determined by reference to the market value of an ADS at the date of grant | ||||
| Number of options over ordinary shares granted (in shares) | 24,711,600 | |||
| Exercise price equal to the nominal value of the ordinary shares | ||||
| Number of options over ordinary shares granted (in shares) | 24,944,376 | 
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- Definition Face amount or stated value per share of common stock. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition Gross number of share options (or share units) granted during the period. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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