Surveying my work in progress from the bedroom window I spotted a fox as it came out of the trees and started to cross the mown patch to the garden. A quick call from my mobile to the landline downstairs to alert the rest of my family. We all watched as it climbed onto and walked along the stone wall then disappeared into the clump of damson trees. That explained the purple scat at the corner of the garden.
The following night I put up a trail camera next to the damsons. Sure enough the fox was back. If you look carefully enough you can see the fox being startled by an owl flying off a post.