Investments in Joint Ventures and Associates - Summary of Financial Statements (Detail) - GBP (£) £ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022
Investments in subsidiaries, joint ventures and associates [abstract]
Associates	£ 22	£ 25
Total	22	25
Associates	1	1
Total	£ 1	£ 1

The amount of investments in associates in an entity's separate financial statements. [Refer: Associates [member]]

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- Definition

The amount of investments in subsidiaries, joint ventures and associates in an entity's separate financial statements. [Refer: Associates [member]; Joint ventures [member]; Subsidiaries [member]; Investments in subsidiaries reported in separate financial statements]

+ References

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No definition available.

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- Definition

The entity's share of the profit (loss) of associates accounted for using the equity method. [Refer: Associates [member]; Investments accounted for using equity method; Profit (loss)]

+ References

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- Definition

The entity's share of the profit (loss) of associates and joint ventures accounted for using the equity method. [Refer: Associates [member]; Investments accounted for using equity method; Joint ventures [member]; Profit (loss)]

+ References

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