poss grey goshawk (white phase) sydney

hi all
a large white bird sent the local miners, magpies and currawongs into a frenzy this afternoon (around 3.30pm) here in sleepy vaucluse not far from vaucluse house by the harbour.
i inadvertently flushed the mystery bird (which departed with a single guttural squawk) but only caught a very fleeting glimpse of it from behind before it disappeared south along the harbour foreshore. 
we get sulphur crested cocatoos here (and YTBCs, bless 'em) but by the local birds' behaviour (distress calls and divebombing) and absence of any cockatoo calls, i would have thought it was a bird of prey. 
the other possibility might be a channel-billed cuckoo but the mystery bird's wings were   lighter and broad/rounded like a goshawk's.
anyhoo, if you're in the area, keep your eyes peeled. independent confirmation would be most welcome. i would also be interested to know if any grey goshawks, esp white phases, have been seen in the city.  
spectacled drongo