Normally, Americans do not require a visa of any sort to visit or transit the UK. However, some Americans are unable to qualify because of an unfavourable history. Others experience discomfort and do not believe they will be able to qualify because of their personal circumstances. Some have been visiting the UK too often and they do not want their transit recorded as a visit (
...will not live in the UK for extended periods through frequent or successive visits...).
So yes, it is possible for an American to apply for leave to enter under the transit visa rules. In order to do this, they must convince the Immigration Officer that their intent is genuine and that they will not abscond and go underground during their transit. Doing this can be difficult however, if the Immigration Officer thinks that the person is attempting to evade controls, the person will be removed to their point of embarkation.
To avoid the inconvenience of a removal from port, an American (actually any non-visa national) can apply for entry clearance beforehand. In the case of transit, the person can take the following steps...
- Create an account at Visa4UK and generate a new application as a
'Visitor in Transit'
- In the final part of the form, make a brief explanation about why
this type of application is being submitted
- At the end of the form, pay the fee and book an appointment for
biometric enrolment (note: this needs to be done for each and every
- Print the form and take it to the biometric centre, enrol in
- Put the application along with all the evidence (including passport)
into a large envelope
- Send the bundle to the British mission in New York...
There are variants of this procedure that allow an application to be upgraded to a priority status. Priority upgrades are handled by UKVI's commercial partner and the instructions are currently at Priority Visa Service. Not every applicant can qualify for priority service.
There is another variant where the applicant can have permanent or sensitive evidential documents returned to them by courier. In order to do this, the applicant must acquire an approved shipping label. All applicants can qualify for this service.
There is another variant for steps 4, 5, & 6 for high net worth individuals, but it's out of scope there.
Most decisions are processed within two weeks. The applicant can opt to receive an email notification, but there are no facilities for an applicant to collect their passport at the consulate (there are exceptions for chauffeurs etc, but this is out of scope here).
There are no appeal rights for short-term applications. If an application is refused, a fresh application starting from square 1 must be made. However, the person does not need to create a new account at Visa4UK.