Red-crested Pochard x Tufted Duck hybrid, Pontefract Park, Pontefract (West Yorkshire, UK), 14th February 2017 - copyright Philip Ridsdale
(photo ID: 3078)
This is a very striking hybrid when seen in good light, though I guess could be overlooked among Tufted Ducks if not seen so well. The strong orange tones to the crown feathers are distinctive (though not very dissimilar to those of a Ferruginous Duck x Tufted Duck hybrid), the back is not jet black and the bill is pinkish. Like Red-crested Pochard x Common Pochard hybrids the rear border of the black breast is sloped down towards the rear of the duck as it is on Red-crested Pochard.
Red-crested Pochard x Tufted Duck hybrid (with Tufted Ducks; same bird as in photo ID 3078 above), Pontefract Park, Pontefract (West Yorkshire, UK), 14th February 2017 - copyright Philip Ridsdale
(photo IDs: 3079-3081)
Joern Lehmhus has written about this hybrid in the German magazine Aves. The text is in German but non-German speakers may still be interested as it's accompanied by a couple of photos of Red-crested Pochard x Tufted Duck hybrids. You can access the PDF of Aves 4 (2013) - the article starts on page 21 with section 2.4 on this hybrid beginning at page 25 - the two photos captioned "Reiherente x Kolbenente" are Red-crested Pochard x Tufted Duck hybrids.
Red-crested Pochard Netta rufina
Tufted Duck Aythya fuligula