Before revision:  Both the Office for National Statistics's respective count of 18,757 death certificates which mention COVID-19, and the Department of Health and Social Care's count of 15,755 in-hospital COVID-19-associated deaths, are appreciably less, implying that their counting methods have underestimated rather than overestimated the pandemic's true death toll.
After revision:  Both the Office for National Statistics's respective count of 18,757 death certificates which mention COVID-19, and the Department of Health and Social Care's hospital-focused count of 21,222 deaths, are appreciably less, implying that their counting methods have underestimated rather than overestimated the pandemic's true death toll.