Rock Pipit with one leg

This little fella is a Rock Pipit, they always catch my eye when I'm walking along the Cobb Wall in Lyme Regis ,they don't seem to bothered by people and fly up to the wall hovering like humming birds picking the bugs out of the Historic Cobb wall.
Also on my slightly worse for ware walks home of a summers night, you can hear the high pitch squeak they make in the dead of night.
This guy only has one leg, apparently so I'm told by my father, that they are susceptible to a disease that only affects them resulting in loosing a leg when they become adult birds. there must be something in this because this morning I saw at least three hopping around on one leg.
This guy was coping ok on just the one, but it was a bit windy and he was knocked over a few times.