Unusual bullfinch

In the garden this morning a male bullfinch that had a pure white 'cap' but still had black around the lower part of it's head. It was with another male and female bullfinch, but seemed larger/bulkier than either of them and was acting aggressively towards the other male. There didn't appear to be any other notible colouring discrepencies except perhaps that the red appeared lighter(?).

Red kite also seen over the garden.