A good lesson for the lad that in many ways, not just to make sure you can undo your own wheelnuts and have a spare wheel jack and wheelbrace handy if you are changing from maker's spec, but longer term to avoid tyre sizes which can't cope with a simple pot hole, indeed some of the alloys on that marque crack via the road shocks transmitted through ridiculously low profile tyres, i don't suppose BMW are alone in this.

One other lesson for you all, a decent trolley jack (not a £30 toy) is a must for any home mechanic, even something which should be as simple as changing a wheel is an infinitely safer job with a proper sturdy trolley jack in place...not as one should trust even that by getting underneath the vehicle without something solid to prevent the car dropping if the hydraulic seal fails.

Have you closely inspected the wheelbolts threads, if they've been done so tight you couldn't shift them i wouldn't be surprised if there's evidence the threads have suffered.

When you refit the (presumably alloy) wheel, explain to him to clean up and put a wipe of coppaslip on the spigot so the alloy doesn't corrode bond to the steel hub making it a nightmare to remove the wheels down the line, sods law dictates punctures don't normally happen as conveniently as that, when you do get a puncture you want that wheel to come off with just a gentle tug not neediing to be hammered off from behind (with the sledge hammer you won't have to hand) necessitating crawling underneath at the side of the road...the breakdown chap if called out will also be grateful for that small mercy.

Edited by gordonbennet on 25/11/2019 at 09:50

I wonder what the pressure in the tyre was before the pothole split it. Had he checked recently? To avoid pothole damage as much as possible it is essential the tyre pressure is at, or even slightly above, recommended pressure - especially those absurd low profile rubber bands, which are just asking for expensive damage to the actual wheel as well as the tyre.