Yes, since the UK is no longer part of the European Union and manages its borders separately, the United Kingdom has its own set of entry and transit requirements. Check with your airline and final destination about potential additional testing, quarantine, or other requirements. UK Transiting and Layover rules: https://www.gov.uk/uk-border-control/layovers-and-transiting Learn more about transiting Heathrow airport here: https://www.heathrow.com/customer-support/faq/coronavirus-covid-19#govt-restrictions