Earnings per share - Summary of earnings per share - 2022, 2021 and 2020 (Details) - GBP (£) £ / shares in Units, £ in Millions, shares in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Earnings per share
Net profit attributable to shareholders	£ 1,781	£ 1,634	£ 1,471	£ 1,224	£ 1,505
Weighted average number of shares, Basic	1,891.8	1,918.5	1,928.0
EPS, Basic	£ 0.941	£ 0.852	£ 0.763	£ 0.635	£ 0.774
Net profit attributable to shareholders	£ 1,781	£ 1,634	£ 1,471
Weighted average number of shares, Diluted	1,902.8	1,929.3	1,939.4
EPS, Diluted	£ 0.936	£ 0.847	£ 0.758

The weighted average number of ordinary shares outstanding plus the weighted average number of ordinary shares that would be issued on the conversion of all the dilutive potential ordinary shares into ordinary shares. [Refer: Ordinary shares [member]; Weighted average [member]]

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The amount of profit (loss) attributable to ordinary equity holders of the parent entity (the numerator) divided by the weighted average number of ordinary shares outstanding during the period (the denominator).

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The amount of profit (loss) attributable to ordinary equity holders of the parent entity (the numerator), divided by the weighted average number of ordinary shares outstanding during the period (the denominator), both adjusted for the effects of all dilutive potential ordinary shares. [Refer: Ordinary shares [member]; Weighted average [member]]

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The profit (loss) attributable to ordinary equity holders of the parent entity. [Refer: Profit (loss)]

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The profit (loss) attributable to ordinary equity holders of the parent entity, adjusted for the effects of all dilutive potential ordinary shares. [Refer: Profit (loss)]

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The number of ordinary shares outstanding at the beginning of the period, adjusted by the number of ordinary shares bought back or issued during the period multiplied by a time-weighting factor.

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