What’s the legality of driving in a carpark...

It’s not legal, but most people do it. You should really be insured and use L plates.

So I could be prosecuted?

Definitely. A car park with public access is classed as a public road even if it is private land.

It's illegal unless you own the car park/have permission from the owner.

Not quite. Driving in a public place without insurance is always illegal, regardless of whether you are the landowner or have the landowner's permission.

But surely a car park is privately owned land? So not technically a public place. If you are the landowner/have permission it must be privately owned.

But surely a car park is privately owned land? So not technically a public place. If you are the landowner/have permission it must be privately owned.

Suppose if you closed it off to the public and you owned the car park you could probably do it, but then I can't imagine OP owns a car park or knows anyone who owns a car park, so it's sort of irrelevant.

In which case I’ll avoid completely

If you're under 17 there are some places around the country like disused airfields that have driving available to 16 year olds, or just wait until you're 17 and do it properly though lessons and learner insurance.

I’m 17

Great, so you can drive legally on the public roads!

If you want to practice on your parents cars as well as lessons then learner insurance is fairly cheap, when I did it it was something like £1 a day.

£1 A DAY??????

you are not going to learn much in a car park, you need a good driving instructor at the start so you do not pick up any bad habits and you can build up your confidence. later when you are more confident you can then look at practising privately but initially i would defo get a good instructor with dual controls