Analysis Of Income And Expense [Abstract]
| Concept |
2021-01-01 to 2021-12-31 |
2021-01-01 to 2021-12-31 |
2021-01-01 to 2021-12-31 |
2021-01-01 to 2021-12-31 |
2021-01-01 to 2021-12-31 |
2021-01-01 to 2021-12-31 |
2021-01-01 to 2021-12-31 |
2021-01-01 to 2021-12-31 |
2021-01-01 to 2021-12-31 |
2020-01-01 to 2020-12-31 |
2020-01-01 to 2020-12-31 |
2020-01-01 to 2020-12-31 |
2020-01-01 to 2020-12-31 |
2020-01-01 to 2020-12-31 |
2020-01-01 to 2020-12-31 |
2020-01-01 to 2020-12-31 |
2020-01-01 to 2020-12-31 |
2020-01-01 to 2020-12-31 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Analysis of income and expense [abstract] | ||||||||||||||||||
| Material income and expense [abstract] | ||||||||||||||||||
| Expense of restructuring activities | — | — | — | — | — | — | — |
259,000,000
GBP
|
— | — | — |
316,000,000
GBP
|
— | — | — | — | — | — |
| Income from continuing operations attributable to owners of parent | — | — | — | — | — | — | — |
994,000,000
GBP
|
— | — | — |
848,000,000
GBP
|
— | — | — | — | — | — |
| Income from discontinued operations attributable to owners of parent | — | — | — | — | — | — | — |
–
GBP
|
— | — | — |
15,000,000
GBP
|
— | — | — | — | — | — |
| Expenses by nature [abstract] | ||||||||||||||||||
| Classes of employee benefits expense [abstract] | ||||||||||||||||||
| Employee benefits expense | — | — | — | — | — | — | — |
604,000,000
GBP
|
— | — | — |
625,000,000
GBP
|
— | — | — | — | — | — |
| Share of profit (loss) of associates and joint ventures accounted for using equity method [abstract] | ||||||||||||||||||
| Share of profit (loss) of associates and joint ventures accounted for using equity method | — | — | — | — | — | — | — |
22,000,000
GBP
|
— | — | — |
194,000,000
GBP
|
— | — | — | — | — | — |
| Share of other comprehensive income of associates and joint ventures accounted for using equity method, before tax [abstract] | ||||||||||||||||||
| Share of other comprehensive income of associates and joint ventures accounted for using equity method that will not be reclassified to profit or loss, before tax | — | — | — | — | — | — | — |
12,000,000
GBP
|
— | — | — |
13,000,000
GBP
|
— | — | — | — | — | — |
| Share of other comprehensive income of associates and joint ventures accounted for using equity method that will be reclassified to profit or loss, before tax | — | — | — | — | — | — | — |
4,000,000
GBP
|
— | — | — |
13,000,000
GBP
|
— | — | — | — | — | — |
| Income tax relating to components of other comprehensive income [abstract] | ||||||||||||||||||
| Income tax relating to components of other comprehensive income that will not be reclassified to profit or loss | — | — | — | — | — | — | — |
3,000,000
GBP
|
— | — | — |
2,000,000
GBP
|
— | — | — | — | — | — |
| Income tax relating to components of other comprehensive income that will be reclassified to profit or loss | — | — | — | — | — | — | — |
3,000,000
GBP
|
— | — | — |
2,000,000
GBP
|
— | — | — | — | — | — |
| Comprehensive income, continuing and discontinued operations [abstract] | ||||||||||||||||||
| Comprehensive income |
–
GBP
|
1,000,000
GBP
|
–
GBP
|
–
GBP
|
22,000,000
GBP
|
–
GBP
|
1,135,000,000
GBP
|
1,136,000,000
GBP
|
1,113,000,000
GBP
|
1,115,000,000
GBP
|
–
GBP
|
1,126,000,000
GBP
|
5,000,000
GBP
|
–
GBP
|
–
GBP
|
–
GBP
|
1,121,000,000
GBP
|
6,000,000
GBP
|