(LOSS)/EARNINGS PER SHARE - Calculation of Basic and Diluted EPS (Details) - GBP (£) £ / shares in Units, £ in Millions, shares in Millions	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Earnings per share [abstract]
Profit for the year attributable to equity holders of the parent (£ million) - Basic	£ (215)	£ 542	£ 110
Weighted average number of shares used in basic EPS calculation (million) (in shares)	1,076	1,077	1,072
Basic EPS (in dollar per share)	£ (0.200)	£ 0.503	£ 0.103
Profit for the year attributable to equity holders of the parent (£ million) - Diluted	£ (215)	£ 542	£ 110
Weighted average number of shares used in diluted EPS calculation (million) (in shares)	1,076	1,097	1,094
Diluted EPS (in dollar per share)	£ (0.200)	£ 0.494	£ 0.101

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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