To my eye, neither of the pair of birds in the top picture, (now titled 'Baer's Pochards') shows any trace whatsoever of the green head described by Scott, and illustrated clearly by the Chester bird (inset) that I remember.
@Andrew Swales An interesting website! I agree that some of the photos of summer plumage ducks and drakes look similar to the birds in the photo. I think we have difficulties because these two birds appear to be partially in moult and neither is at the correct angle to show all their plumage: a slight sign of green on the drake's head would convince me that they are Baer's, but as I said previously, that can be hard to see. It always helps to have 2 or 3 photos if you are trying to identify an animal - and sometimes you still cannot be certain.