When I saw a pair of these on the River Nene at Titchmarsh I couldn't decide if they were Geese or Ducks ........

What do you think ?

So some homework was required.

It was the second image and assistance from the ID section of Birdforum ( with thanks to Stevethehydra - Full name not known )  that finally clinched it.

The conclusion is that it is certainly a duck and close to ( if not a pure example ) of the Aylesbury breed - a "heavy" duck which is a lot larger than the wild-type Mallards that it was ultimately selectively bred from. 

People are often surprised by the size of "heavy" domestic ducks!