I guess a domestic escapee at Snettisham RSPB car park!
No interactions present.
There are lots of "crosses" between wild mallards and domestic ducks - most of which were bred from this species - out there. (And yes, before someone else points it out, I know they aren't proper crosses, being essentially the same species. Inter-racials, perhaps?)
Google "manky mallards" for lots of examples.
Lat/Lng: 52.8835, 0.4572
OS grid ref: TF654346