Another hybrid duck in Rowheath park this afternoon, again happily associating with the Mallards and very approachable.
Noticeably small (the second photo shows it's about the same size as a Coot) and small-billed. Curled tail feathers and general appearance suggests some Long-Tailed Duck heritage at some point?
Judging by the size, I'd say it's got small "Call Duck" ancestry. (A minature Mallard-derived strain, very vocal and used as decoy ducks to call in wild birds), the curled tail feathers are typical for drake Mallard, although they do look very obvious on this individual. They come in a variety of colours from wild-type to pure white with just about anything in between possible.