Hey JPTSharma: Well, from my experience this year, I can tell you that,for sure, you will need a Transit Visa to fly via London, unless you are citizen of a certain countries, which are exempt, and of course if you have a Green Card. I was trying to fly via London this year, but since I needed a transit visa and applying transit visa here, where I live, will take forever to make and also I have to pay an additional fees for that, so I decided to take via Paris. So, the moral of the story, you need a Transit Visa to fly via London unless you fall under a catagory of exempt. Have a safe trip and nice one too. RSVP