On Sat, 3 Feb 2018 21:38:34 +0000
Simon T wrote:

However, what's troubling me is why did that one paricular tile come
loose?

A few weeks back the wind picked up a builder's bag next door and
thrashed it around, creating a few bits of broken tile (I don't think
any of them were ours, from what I could see they slid into our drive
from next door's roof).