Upvote:-1
From the site in the Duplicate:
If you will be passing through Customs:
Leaving the airport
Apply for a Visitor in Transit visa if youβll be going through UK border control but leaving the UK within 48 hours.You can also apply for a long-term Visitor in Transit visa if you can prove you need to frequently pass through the UK over a longer period.
Otherwise, if only a Gate Change is needed:
You should apply for a Direct Airside Transit visa if youβll be changing flights in the UK without going through immigration control.
Upvote:1
NO, you don't need a UK visa. Simple.
It's very plain and simple and honestly I don't understand why the wording is confusing you. As the Gov.UK website mentions for your conditions,
- are travelling from Australia, Canada, New Zealand or the USA and itβs less than 6 months since you last entered that country with a valid entry visa
That's it. This condition applies to you and exempts you from the transit visa requirement. Nothing else matters after this anyway. The I-797 story you mentioned is for US Permanent Residents who are waiting for their Residency Card to be renewed.
You have a valid US visa, period. You don't need a UK visa (only to transit, so you should not try to cross border control with this i.e. you cannot enter the UK, you can only remain in the transit region of the airport).