For anyone who’s interested, I recently had a pupil who was driving on their full licence from another country inside the 12 month period they are allowed. They had a UK provisional licence, and were taking their test in their own car.
The question arose over what would happen if they failed their test. Would they be legally allowed to drive away?
I emailed DVLA, and they replied:
A non GB licence holder can still drive for up to 12 months regardless of a UK test failure.
Essentially, they could fail their test 20 times and still be allowed to drive alone on their non-UK licence inside that 12 months as long as the licence remained valid. I know that will get a lot of Brexiters hot under the collar, but it’s the way it is.
It is not voided when they obtain a provisional licence, which makes sense, since the intended purpose of that 12 month period is to give them time to pass a UK test.