Pensions - Amounts in the Financial statements (Details) - GBP (£) £ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Pensions
Fund assets at fair value	£ 57,249	£ 51,925	£ 48,752	£ 49,746	£ 49,229
Present value of fund liabilities	48,864	44,115	39,607	42,378	43,990
Funded status	8,385	7,810	9,145	£ 7,368	£ 5,239
Net assets of schemes in surplus	723	614
Net liabilities of schemes in deficit	(121)	(119)
Retirement benefit liability	602	495	355
Asset ceiling/minimum funding
Pensions
Retirement benefit liability	£ (7,783)	£ (7,315)	£ (8,790)

The amount of assets of a retirement benefit plan less liabilities other than the actuarial present value of promised retirement benefits.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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The present value, without deducting any plan assets, of expected future payments required to settle the obligation resulting from employee service in the current and prior periods. [Refer: Plan assets, at fair value]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table.

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The amount of deficit or surplus in a defined benefit plan, adjusted for any effect of limiting a net defined benefit asset to the asset ceiling. [Refer: Defined benefit plans [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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The fair value of defined benefit plan assets. Plan assets comprise assets held by a long-term employee benefit fund and qualifying insurance policies. [Refer: At fair value [member]]

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The fair value of any plan assets, less the present value of the defined benefit obligation. [Refer: Plan assets [member]]

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The actuarial valuation of benefit plans in deficit.

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