No interactions present.
they often have white ("leucistic", I think) patches. These can survive moults, and make individuals distinctive.
Update - I must have been typing this as the identification above was added!
There is a survey of odd plumages at http://bto-enews.org/IG4-MRY7-39HGCA-8T6ZQ-1/c.aspx .
recording wildlife with The Recorder's Year on www.hbrg.org.uk/TRY.html.
Lat/Lng: 51.38049, -2.42611
OS grid ref: ST704646