gerekmiyor.
www.ukvisas.gov.uk
"You will be exempt from the DATV requirement and may be able to transit without visa if you hold one of the following.
* A valid visa for entry to Australia, Canada, New Zealand or the United States of America and a valid airline ticket for travel through the UK as part of a journey from another country or territory to the country for which you have the entry visa.
* A valid visa for entry to Australia, Canada, New Zealand or the United States of America and a valid airline ticket for travel through the UK as part of a journey from the country for which you have the visa to another country or territory.
* A valid airline ticket for travel through the UK as part of a journey from Australia, Canada, New Zealand or the United States of America to another country or territory, as long as you do not transit (pass through) the UK on a date more than six months after the date on which you last entered Australia, Canada, New Zealand or the United States of America with a valid visa for that country."
kısa öz türkçe meali:
hava alanları uluslararası alanlardır ( pasaport kontrolünden geçtikten sonra), pasaport kontrolünden çıkmadığın müddetçe ( ki o durumda çıkamazsın) istediğin kadar kalabilirsin.