I spotted this in Carlisle City Centre and the closest thing I could find by briefly researching it was 'pigeon bumblefoot' but I just wanted to get an expert opinion because I'm not convinced that's what it is from my research.
Thanks for any help.
2013 photos & vids here
eff37 on Flickr
Without seeing the pidge first hand I'd say this is 'stringfoot', which is essentially 'bumblefoot' in that it's the result of an infection caused by standing in their own poop when there is a foot injury. Many ferals can adapt and survive with this type of issue. If there is a pigeon friendly rescue near you and you can catch the bird, they might be able to remove the damaged parts or even amputate. Try www.helpwildlife.co.uk to see if there is a local rescue. I would advise against taking it to a vet.
Unicum arbustum haud alit duos erithacos
(One bush does not shelter two Robins)
Zenodotus (3rd Century B.C.)