Does anyone have any ideas as to this bird's likely parentage?
No interactions present.
Why not consider Bar-headed Goose (Anser indicus) as the other parent?
The orange legs and many plumage features would fit - and the observer also posted an observation of a Bar-headed Goose seen at the same location on the same day.
Lat/Lng: 50.8468, 0.1764
OS grid ref: TQ533075