Day 121/24. You can see where they get their name.

This is a Shield Bug. You can certainly see where the name comes from.
This exact type is a Sloe Bug dolycoris baccarum. They are very common in our garden in Southern Hampshire. It's easy to find them on a sunny day.
In america these are called stink bugs as they are supposed to emit a foul smell if threatened. I've never noticed a smelly one. If I get too close they usually just fly away.