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im going to travel from Hyderabad to Vancouver on 20th august, and will be passing through heathrow. My layover time being 14hrs, will I require a transit visa? I have a valid canadian study permit, but will be arriving at heathrow on 20th and leaving on 21st. I do not have any intention to go out for a visit and also don't need to go through immigration. please help, i dont have much time!