Common Gull with leg twisted through tail

This Common Gull, which has visited the garden on a couple of occasions, has a malformed right leg which appears to be twisted around and facing backwards. In flight this leg pierces through the feathers of the tail and this has caused an area of severe feather damage and wear within the tail and coverts.

In plumage the bird resembles a first winter (1CY), apart from a single white adult-type tail feather. 

When on the ground the bird has a more awkward hopping gait but it does appear to be able to feed reasonably well. I'll keep an eye out for it, though given that it has survived the recent severe weather, maybe it is well able to look after itself...