Hi, I am a Bangladeshi citizen and I have a valid student visa of Canada. I have a flight from Halifax to Dhaka; which has a transit in LHR (layover for 21hrs) . Do I need a transit visa ?
Probably not. As long as your next flight is before midnight on the day after you arrive. So let's say you land in Heathrow on Sunday at 11 PM Local Time. Your next flight needs to leave before midnight on Monday - and with a 21 hour layover, it will.
You should double check with your airline to make sure you don't run into any issues. Also, if your onward flight gets delayed by a few hours.. I'm not sure what happens. Logic says that the UK will still let you leave, but you never know with immigration. You should double check with the airline, and if you can get a flight with a shorter layover.. you should.
1. Transiting without a visa
You might be eligible for ‘transit without visa’ if:
you arrive and depart by air
have a confirmed onward flight that leaves on the day you arrive or before midnight on the day after you arrive
have the right documents for your destination (eg a visa for that country)
One of the following must also apply:
you’re travelling from (or on part of a reasonable journey from ) Australia, Canada, New Zealand or the USA and have a valid visa for that country