I?m not certain that?s right. This is from UK Gov website: Your isolation period includes the day the first person in your household?s symptoms started (or the day their test was taken if they did not have symptoms, whether this was an LFD or PCR test), and the next 10 full days. This means that if, for example, your 10 day isolation period starts on the 15th of the month, your isolation period ends at 23:59 hrs on the 25th and you can return to your normal routine. https://www.gov.uk/government/publications/covid-19-stay-at-home-guidance/stay-at-home-guidance-for-households-with-possible-coronavirus-covid-19-infection#main-messages