I was so surprised in France recently to see a small bee fly past me while clutching a leaf. I’d never seen anything like it. It almost looked as though it was riding a little green magic carpet.
Then the bee landed on a stone wall and tried to push the leaf into a small crevice in the wall. After several attempts it managed to get the leaf right into the crevice. A few moments later it returned with another leaf and pushed that one into the crevice as well.
It seems this is a leaf-cutter bee. These are solitary bees. They cut disks out of leaves and use them to make their nests in holes in walls, like the bee I saw, or in wood. Drilling holes in a piece of dead wood can encourage them. They are, apparently, found in the UK as well, and are good pollinators. So keep your eyes open for these wonderful little bees!