My wife noticed this on her trousers immediately after coming home - probably acquired after brushing past a bush. It's about one inch long, and does not move much - but when poked it will flex and appear to try to roll.
It looks for all the world like a stick - but I've googled "stick insect", and this doesn't seem to have enough (or the right kind of) legs.
We live in England, in a suburban setting. We both work in offices and don't have a lot of contact with nature.
Apologies for the quality of the photo; I can try to take a better one if it would help to get another angle.