It's just the alternator belt. Car would be programmed to tell you to stop immediately as some water pumps are belt driven so there's a risk of over heating and obviously emptying the battery.
I can't imagine there's any lasting damage done there, just an annoying job to untangle the old belt.
I’m around 60 seconds from home, but the dash flashed up “stop immediately”, so that’s what I did. I imagine a new engine would be expensive.
Still, glass half full, if I do need a new engine we may as well shoot for 700 bhp.