yep - very convincing. Have later found out that there was definitely an escaped Chiloe Wigeon at the site a few years back. Thanks guys.

Certainly at least part Chiloe Wigeon

Here's an article on Eurasian/Chiloe Wigeon hybrids - the 1st pic is rather convincing:

http://birdhybrids.blogspot.com/2014/03/eurasian-wigeon-x-chiloe-wigeon.html

Visited a small reservoir in Cambridgeshire today...and found this duck loosely associating with the masses of Wigeon, Pochard and Tufted Duck. Not really sure what it is - hybrid, domesticated, species etc? Was seen to dabble as opposed to dive, didn't see it fly but didn't see any of the ducks fly for that matter.

Any help with ID would be welcome.