Property, Plant and Equipment - Summary of Property, Plant and Equipment (Detail) - GBP (£) £ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure of detailed information about property, plant and equipment
At start of year	£ 126
Charge for the year	(43)	£ (47)	£ (52)
At end of year	99	126
Cost
Disclosure of detailed information about property, plant and equipment
At start of year	618	683
Acquisitions	1	1
Capital expenditure	30	36
Disposals	(118)	(159)
Exchange translation differences	(24)	57
At end of year	507	618	683
Accumulated depreciation
Disclosure of detailed information about property, plant and equipment
At start of year	(492)	(552)
Charge for the year	(43)	(47)
Disposals	108	154
Exchange translation differences	19	(47)
At end of year	(408)	(492)	(552)
Land and buildings
Disclosure of detailed information about property, plant and equipment
At start of year	51
At end of year	42	51
Land and buildings \| Cost
Disclosure of detailed information about property, plant and equipment
At start of year	166	167
Acquisitions		1
Capital expenditure	5	3
Disposals	(30)	(19)
Exchange translation differences	(7)	14
At end of year	134	166	167
Land and buildings \| Accumulated depreciation
Disclosure of detailed information about property, plant and equipment
At start of year	(115)	(111)
Charge for the year	(5)	(6)
Disposals	23	12
Exchange translation differences	5	(10)
At end of year	(92)	(115)	(111)
Fixtures and equipment
Disclosure of detailed information about property, plant and equipment
At start of year	75
At end of year	57	75
Fixtures and equipment \| Cost
Disclosure of detailed information about property, plant and equipment
At start of year	452	516
Acquisitions	1
Capital expenditure	25	33
Disposals	(88)	(140)
Exchange translation differences	(17)	43
At end of year	373	452	516
Fixtures and equipment \| Accumulated depreciation
Disclosure of detailed information about property, plant and equipment
At start of year	(377)	(441)
Charge for the year	(38)	(41)
Disposals	85	142
Exchange translation differences	14	(37)
At end of year	£ (316)	£ (377)	£ (441)

The increase in property, plant and equipment resulting from acquisitions through business combinations. [Refer: Business combinations [member]; Property, plant and equipment]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 16
-IssueDate 2023-01-01
-Paragraph 73
-Subparagraph e
-Clause iii
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=16&code=ifrs-tx-2023-en-r&anchor=para_73_e_iii&doctype=Standard
-URIDate 2023-03-23

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- Definition

The amount of additions to property, plant and equipment other than those acquired through business combinations. [Refer: Business combinations [member]; Property, plant and equipment]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 16
-IssueDate 2023-01-01
-Paragraph 73
-Subparagraph e
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- Definition

The amount of depreciation of property, plant and equipment. [Refer: Depreciation and amortisation expense; Property, plant and equipment]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 16
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-Paragraph 73
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 16
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Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with members defined in one or many axes of the table.

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No definition available.

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- Definition

The decrease in property, plant and equipment resulting from disposals. [Refer: Property, plant and equipment]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 16
-IssueDate 2023-01-01
-Paragraph 73
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- Definition

The increase (decrease) in property, plant and equipment resulting from net exchange differences arising on the translation of the financial statements from the functional currency into a different presentation currency, including the translation of a foreign operation into the presentation currency of the reporting entity. [Refer: Property, plant and equipment]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 16
-IssueDate 2023-01-01
-Paragraph 73
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- Definition

The amount of tangible assets that: (a) are held for use in the production or supply of goods or services, for rental to others, or for administrative purposes; and (b) are expected to be used during more than one period. Note that right-of-use assets are not included. [Contrast: Property, plant and equipment including right-of-use assets]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
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