Now all of us, will have visa stamped on our passport although it’s single entry visa. Without valid visa stamped, even our home country immigration will not allow to board any international flight. Last week, my colleague travelled to USA on business visa using same flight till London and she was not asked for transit visa. So, there is lot of ambiguity on this topic, so raised enquiry with British embassy, hopefully will get response.
Now
Checked UK Govt website and found following information :-
Check if you need a UK visa
You’ll need a visa to pass through the UK in transit (unless you’re exempt)
You should apply for a Direct Airside Transit visa if you arrive in the UK on a flight and leave again without passing through immigration control.
Exemptions
You don’t need a visa if you have one of the following:
- a visa for Canada, New Zealand, Australia or the USA (this can be used for travel to any country)