Hi, I am traveling to India from USA in September 2018 (Carrier- British Airways). I have a 4 hour layover in London Heathrow Airport and I'll be departing from the same terminal to India. Currently, I'm on a H1B visa since April 2018 (not yet stamped) and I'm going to get my visa stamped in India. My F1 visa is valid till July 2020 and I also have my B1/B2 visa valid till August 2024. Do I need a Direct Airside transit visa to travel via London or am i good to travel with the valid F1 visa stamp on my passport? I got ambiguous responses from the airlines and the UK embassy site states that I need a valid visa to USA. Kindly help me with the query.