Flat tyre

I had my first completely flat tyre yesterday and had to swap it for the spare. In the past it’s always been a slow puncture and I’d been able to get to the petrol station to pump it up again or to the garage to get it replaced before it got completely flat.
It took me a little while to figure out how to get to the spare tyre and where the locking wheel nut key was, but I got there in the end.

When I took the old tyre off, this is what I found.
flat tyre with large metal piece in it
It’s no wonder the tyre went flat!