Driving permit question for a vespa scooter?

I'm living in the UK on a long-term work permit and have put off getting a driver's license here due to the insurance costs and general hassle of owning a car. But I'm now considering buying a Vespa scooter to get around town. My understanding is that one only need's a 'learner's license' for scooters that have certain engine capacities (up to 125cc?), but I've not found any clear information about this online. Also, I know I'd have to take a CBT test, but do I first need to have a learner's license before this? Incidentally, I've had a US driver's license for about 16 years, so I'm not a new driver in general, just to the UK... Thanks.

if you have a full us license can you not drive here legally,you will be ok if so.if not you'll need a provisional licence and cbt before you can ride

You will need a full licence to drive a 125.
You can drive a 50cc on a provisional licence.

your U.S. licence will not cover you in the U.K. you will need to apply for a provisional licence before you take a CBT and the CBT will last you 2 years. when this runs out there used to be a waiting period before you could take it again but this has now been stopped.

generally you need a provisional licence before doing your cbt .