I would be travelling to the US with H4 visa (first time travelling to the US) through London HT. I came across in the gov.uk site that a Valid US visa holder does not require a transit visa.
"You are exempt from needing a transit visa if you are travelling to the US, Canada, Australia or New Zealand and have a valid visa for this country"
Is an H4 visa (without any prior port of entry stamping)considered a valid US visa? Do I have to get a Transit visa?
