Out walking along a canal towpath, I just saw this, on the far side of the canal. Looked away and something in my head said, look again. I did, but it was a long way away. Only had a shortish lens on my camera, so took a photograph and magnified it on the back of the camera. I was quite surprised my initial idea was correct. It is a non native Terrapin, probably an ex pet, illegally released when it got too big to look after. It looks tiny here but was probably a minimum of twelve inches in length.
This is cropped.
A neighbour once told us that she had found a tortoise by a local river, and wasnt sure what to do with it. @shepherdmanswife offered to adopt, but on arrival it turned out to be a red-necked terrapin. After a lot of phone calls we found someone licenced to rescue such "exotics", and we wondered how far we would need to travel to deliver the terrapin. Turned out he was just a mile away in our local village!