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If you 'google' species like White-fronted Goose, or check in a bird book, you will see that they are far slimmer and less heavy than these birds, which you have seen at Whitlingham Marsh.
Wild Geese are nesting up in the arctic and then flying south to winter here. These heavy domestic breeds (which are closest to Greylag Geese) would struggle to fly the length of my living room! :)
Often, birds like this have had their wings clipped, too, and so seem very short-winged.
My Flickr photos...
There seems to be one 'Greylag' Goose breed recognised by the British Waterfowl Association that has the black tip to the bill seen here; the Steinbacher, which should typically also show more black on the cutting edges of the bill - and the origins of this breed are believed to involve some cross breeding with "Chinese" (ie. domestic Swan Geese).
The BWA breed standards handbook, mentions that it is quite common to find first generation hybrids of Chinese and 'western' geese that closely resemble this breed in most respects.
...with you, Roy, basically. However, it still contains Greylag, and that is all I was suggesting, against White-fronted, which this clearly is not.
I shall agree with you, in an attempt to update the ID, though I don't really have the precise knowledge of goose hybrids to be definite in my agreement with you on this.
Lat/Lng: 52.6231, 1.3364
OS grid ref: TG259080