Hello everyone
I Am an Indian National and have got a US F1 visa. I have booked Delta Airlines flight which has a 3 hr layover at London Heathrow. I want to ask if I will need a transit visa or not ? As per the official UK visa website, I am exempted as I have a US Visa. However, one Delta airline chat rep said I would need while other one said I would not need a transit visa.

Thank you in advance for your help.