isn't there more to this (and the lad's mate, the car's owner, might be in trouble too)? If the car was on the road and the owner stopped taxing and insuring it, then shouldn't it have been SORN'd? ie. don't you legally need to insure a car if it's not sorn'd (even if you're not using it)?
Either his mate knew he was using the car, so he knew a SORN'd car was on the road or he didn't know it was being used, so the car was arguably stolen?
tbh, I read the original post slightly differently. Lad had insurance on his own car, and I could guess he was using his mate's under DOC cover. smashed it, only covered 3rd party, so unable to claim that ding (and a £2k ding on a £5k car is a pretty major ding). His own insurance died when his car was written off, thus leaving him driving this car uninsured.
I'd guess it would have only been flagged to the police if the registered owner on the v5 didn't have tax or insurance, and thus another problem if it's not sorn'd.
If it's not been sorn'd and the owner has no tax or insurance, won't it be impounded (and/or crushed) anyway? and vice-versa - sorn'd car being on the road?
I kinda think both the lad and his mate are in the proverbial and chances are the car is lost anyway.
If a car needs to be insured and taxed by the registered keeper, then I'd guess the impound would need to see proof of that, instead of anyone else turning up with their own insurance?