Walking to work this morning I saw what I thought was a large thrush from the back, but then I glimpsed a large red chest, so I took a double take - certainly nothing that I'd seen before. It had a clear dash of white under its eye, a dark head, and was on frosted grass beside a suburban road in Leeds, West Yorkshire. I am very far from a bird expert, but having been looking at pictures of red breasted birds, it absolutely looks like an American Robin - except that the white dash under the eye was a straight line, whereas in pictures it seems curved; and I didn't notice white above the eye. What else might it have been? I understand that American Robins are extremely rare in the UK, though not unknown, so it's far more likely to have been something else. Any ideas?