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OTHER RESERVES (Details) - Schedule of Capital Redemption Reserve - Capital redemption reserve [member] - GBP (£)
£ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
OTHER RESERVES (Details) - Schedule of Capital Redemption Reserve [Line Items]      
Beginning Balance £ 4,273 £ 4,115 £ 4,115
Shares cancelled under share buyback programmes (see below) 189 158
Ending Balance £ 4,462 £ 4,273 £ 4,115