With direct airside transiting, as you will not be deemed to have entered the UK, you will not need permission to enter the UK for this type of journey. However, as a visa national, you may still need a Direct Airside Transit visa (DATV) for an airside layover. Not all visa nationals are required to apply for a DATV.

If you already hold a valid UK Standard Visitor Visa, you generally do not need a separate transit visa to pass through the UK. Your existing visa allows you to enter the country, which inherently covers both "airside" transit (staying behind security) and "landside" transit (passing through border control to change airports or stay in a hotel). However, in 2026, the rules for those without a UK visa have changed significantly with the enforcement of the Electronic Travel Authorisation (ETA). If you are a national of a country that normally requires a visa but you are only transiting, you would usually need a "Direct Airside Transit Visa" (DATV) or a "Visitor in Transit" visa. But because your Standard Visitor Visa is a higher-level document, it supersedes these requirements. Always ensure your UK visa is still valid and has remaining entries (if it’s a multiple-entry visa) before your trip. It is also wise to check if your onward destination requires its own visa, as UK airline staff are required to verify your eligibility for the final country on your itinerary before letting you board.