Here it is from the latest covid summary - the proportion of deaths involving covid that were due to covid (as judged by the doctor) ranges from 68% in may 21 to 95% in April 2020.
https://www.ons.gov.uk/peoplepopulationandcommunity/healthandsocialcare/conditionsanddiseases/articles/coronaviruscovid19latestinsights/deaths

"The proportion of deaths involving COVID-19, where COVID-19 was the underlying cause decreased between November and December 2021 in both England (from 84.9% to 83.8%) and Wales (from 83.9% to 79.6%).

These proportions generally correspond with periods of high or low numbers of deaths. In England, the proportion of deaths involving COVID-19 that were also due to COVID-19 was highest in April 2020 (95.2%) and lowest in May 2021 (68.8%). In Wales, this proportion was highest in April 2020 (94.1%) and lowest in June 2021 (42.9%).

The doctor certifying a death can list all causes in the chain of events that led to the death, and pre-existing conditions that may have contributed to the death. Deaths with COVID-19 mentioned anywhere on the death certificate are defined as deaths involving COVID-19. Deaths where COVID-19 is also the underlying cause of death are defined as deaths due to COVID-19.

Last updated: 21/01/2022"