Is there a way to find out if I need a transit visa for a stopover in the UK?

Why yes there is.

This UK government site will tell you if you need a visa to transit through the UK. You enter your nationality, your destination and all the visas you already have, and it will tell you whether you need a transit visa or not. It also includes instructions for making the request.

In summary (but check the exceptions):

  • You must arrive and depart by plane, and your outbound flight must be booked and confirmed.
  • You do not need a transit visa if you do not need a visa for a sightseeing tour in the UK.
  • A transit visa comes in two forms: a 24-hour DATV, and you have to stay on the airside (that is, can not pass immigration) and A transit visitor visa valid for 48 hours and change airport (and terminal in airports where you can not make this trip by plane).
  • You must have all the necessary documents for your final destination, including visas.
  • You are not required to require a transit visa under certain conditions. These can be found at https://www.gov.uk/check-uk-visa. As of September 26, 2018, the conditions are as follows:

Exemptions

You do not need a visa if you have one of the following:

  • a visa for Canada, New Zealand, Australia or the United States (this can be used to travel in any country)
  • a residence permit issued by Australia or New Zealand
  • a common-format residence permit issued by a country of the European Economic Area (EEA) or Switzerland
  • a residence permit issued by Canada after June 28, 2002
  • a uniform type D visa to enter a country of the European Economic Area (EEA) or Switzerland
  • an Irish biometric visa (marked "BC" or "BC BIVS" in the "Remarks" section)
  • a group tourist visa to the Schengen approved destination scheme (ADS) when its holder goes to the Schengen country which has issued the visa
  • a plane ticket from the Schengen Area, if you can prove that you have entered the Schengen Area in the last 30 days on the basis of a valid Schengen ADS visa
  • a USA I-551 valid temporary immigrant visa issued by the United States (a wet ink stamp version will not be accepted)
  • a valid US Permanent Resident Card issued by the United States effective April 21, 1998
  • an expired US permanent residence card I-551, issued by the United States on or after April 21, 1998, with a valid letter I-797 authorizing the extension
  • an independent US 155A / 155B immigration form issued by the United States (attached to a sealed brown envelope)

All visas and residence permits must be valid.


You may be eligible for "visa-free transit" if:

To transit without visa

You may be eligible for "visa-free transit" if:

  • you arrive and go by plane [and]
  • have a confirmed flight departing on the day of your arrival or before midnight the day after your arrival [and]
  • have the right documents for your destination (for example, a visa for this country)

One of the following must also apply:

  • you are traveling (or part of a reasonable trip) to Australia, Canada, New Zealand or the United States and you have a valid visa for that country
  • you have been traveling (or part of a reasonable trip since) to Australia, Canada, New Zealand or the United States and you have a valid visa for that country
  • you have been traveling (or part of a reasonable trip since) to Australia, Canada, New Zealand or the United States and less than six months have elapsed since your last entry into this country with a valid entry visa
  • you have a residence permit issued by Australia or New Zealand
  • you have a common-format residence permit issued by a country in the European Economic Area (EEA) or Switzerland
  • you have a residence permit issued by Canada issued after June 28, 2002
  • you have a uniform D-type visa to enter an EEA country or Switzerland
  • you have an Irish biometric visa (marked "BC" or "BC BIVS" in the "Remarks" section) and a continuation flight ticket to the Republic of Ireland
  • you are from the Republic of Ireland and it has been less than three months since the last authorization was granted to you, under the possession of a valid Irish biometric visa, to land or be in Ireland
  • you have a valid US permanent resident card issued by the United States as of April 21, 1998
  • you have a valid USA I-551 temporary immigrant visa issued by the United States (a wet ink stamp version will not be accepted)
  • you have an expired US I-551 permanent residence card, issued by the United States on or after April 21, 1998, with a valid letter I-797 authorizing the extension
  • you own a US 155A / 155B self-contained US immigration form issued by the United States (attached to a sealed brown envelope)

You will not be able to transit without a visa if a Border Force officer decides that you are not eligible under the Immigration Rules. You can apply for a transit visa before leaving if you do not know if you have the right to transit without a visa.

Electronic visas or electronic residence permits are not accepted to pass visa-free immigration control.

All visas and residence permits must be valid.

Australian paper confirmation slips are not accepted.

If you need more information than provided by this website, you should contact your airline or contact UKVI. The Home Office Billing Procedures – Guide for Carriers also provides guidance on the most subtle points of the rules (it is intended for professionals, not passengers, but explains in detail when a visa is required or not).

Air crossing

In London Heathrow, London Gatwick and Manchester, if you are traveling out of the United Kingdom or Ireland and go to another country (neither the United Kingdom nor Ireland), it is possible to transit without entering in the UK and through UK border control, you can stay on the airside. There is no airside hotel and the transit areas are closed at night. If you have a stopover, you have to go through the UK border control. A detailed guide is available on the website of Heathrow Airport.

People with a valid British visa type with a transit visa do not need an additional visa. This means that the person can pass through a category "C" (visitor), a category "D" (PBS), etc.

The policy is not available on the net. I wrote to the police using my lawyer hat and got this answer …

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They are thinking on the inclusion of this in the written guidelines. Maybe they're going, maybe they're not going.