Yes, I have put 'probable' and not 'possible'!
Unfortunately, I did not see the bird (I was over in the broads and decided safety first!), however, it does sound very interesting! As per DA: the bird is a juv, it does not have a chin strap, but then many don't; he observed the beginning of a vent strap, although couldn't be sure that it met - although others say that it did; there was no white 'triangle' on the flanks, observed both whilst swimming and preening. The only issue seems to be the head shape, which appears angular, although the bill size was probably alright.
I am unable to get out there until Tuesday now, but hopefully others will take it seriously enough to check it out tomorrow. It seems that a number of locals have now seen it and find it 'significantly interesting' ie non committal speak for 'it looks good'! But few people traveled any distance!
Norfolk Bird Info to: