Using Your US Driver's License in the UK

For the few brave souls that want to drive on the wrong left side of the road, you can officially use your American drivers license for up to a year after you have established residency.  After that you are supposed to apply for a British license.  This is mostly because there is not a standard driving test in the US.  Each test differs based on the state where you lived. And instead of the reviewing all state driving requirements to see if they satisfy British standards, the government here has decided to just make all Americans go through the entire process.  I suppose its easier.  But its also a pain in the ass. 

If you obtain a provisional license during this period, you are not subject to provisional license conditions.  You can just go and take the driving test.  But if you fail, the test, then you have to go through the whole process again and provisional license conditions will apply.  These include things like having a learner's tag put on your car as well as having restrictions where you can drive and with how many people.  So if you get your provisional license before your 12 mos are up, BE SURE TO PASS THE TEST! Unless, you really want to take it again.

You could also just risk it and assume that if you get pulled over the police really have no way of knowing how long you've been in the country.  But I wouldn't risk it.

For more info: Directgov