It's Mr.! Larger in large...
I was back in London this weekend, and managed to swing by Eagle Pond to see the Goosles: Mrs. is still sitting on her nest, so I didn't manage to see her, and Mr. is in guard-Goosle mode... He was initially mooching on the island and wouldn't come ashore even when I called out to him (not that that ever works...); I swung by Mount Pond to see what was going on there, and then went back to Eagle Pond to find Mr. taking to the water and circling the pond to check the perimeters. Perhaps the eggs are soon to hatch? He was definitely being very cautious and cagey.
I've put up several other shots on Flickr (album found here).
Mallard (f) close up
Mallard (m) preening (click right for a few more)
A Goosle approacheth
Golden Goosle (and another)
Mr. and repetitive reflections (click right for a few more)