In my view
The tiles on the garages opposite our house, like most here, are only fixed by their own weight, and the odd extra stone at the edges. They interlock, one line curve upside, the next curve down. So simple, so effective. Replacing a few today took two guys (one to hold the ladder and watch) about half an hour at the most.
I thought he was writing me a message at first!
I suppose they'll mellow with age. Don't we all :)