Share-based payments - Narrative (Details) £ in Millions	12 Months Ended
Dec. 31, 2025 GBP (£) shares year	Dec. 31, 2024 GBP (£) shares
Disclosure of terms and conditions of share-based payment arrangement [line items]
Total liability arising from cash-settled share-based payments transactions \| £	£ 15	£ 10
Sharesave
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options exercisable (in shares) \| shares	4,323,541	828,340
Sharesave \| Bottom of range
Disclosure of terms and conditions of share-based payment arrangement [line items]
Contractual life \| year	3
Expected volatility	29.04%
Risk free interest rates	3.47%
Pure dividend yield rates	1.99%
Repo rates	(0.60%)
Sharesave \| Top of range
Disclosure of terms and conditions of share-based payment arrangement [line items]
Contractual life \| year	5
Expected volatility	26.48%
Risk free interest rates	3.56%
Pure dividend yield rates	2.14%
Repo rates	(0.69%)
Share Value Plan / Deferred Share Value Plan
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of options exercisable (in shares) \| shares	0	0
Share Value Plan \| Vesting period one
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period	3 years
Share Value Plan \| Vesting period two
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period	4 years
Share Value Plan \| Vesting period three
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period	5 years
Share Value Plan \| Vesting period four
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period	7 years
Share Value Plan \| Holding period
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period	2 years

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- Definition

Share-Based Payment, Vesting Period

+ References

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- Definition

The expected volatility of the share price used to calculate the fair value of the share options granted. Expected volatility is a measure of the amount by which a price is expected to fluctuate during a period. The measure of volatility used in option pricing models is the annualised standard deviation of the continuously compounded rates of return on the share over a period of time.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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The option life of share options granted.

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The implied yield currently available on zero-coupon government issues of the country in whose currency the exercise price for share options granted is expressed, with a remaining term equal to the expected term of the option being valued (based on the option's remaining contractual life and taking into account the effects of expected early exercise). [Refer: Government [member]]

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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.

+ References

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The percentage of an expected dividend used to calculate the fair value of share options granted.

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- Definition

The amount of liabilities arising from share-based payment transactions. Share-based payment transactions are transactions in which the entity: (a) receives goods or services from the supplier of those goods or services (including an employee) in a share-based payment arrangement; or (b) incurs an obligation to settle the transaction with the supplier in a share-based payment arrangement when another group entity receives those goods or services. [Refer: Types of share-based payment arrangements [domain]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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- Definition

The number of share options exercisable in a share-based payment arrangement.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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