This is a White-throated Needletail, otherwise known as a Spine-tailed Swift. It is the largest of the swifts and we had a flock overflying the house this morning.
According to the book, What Bird is That? by Neville W. Cayley, they breed in Siberia, Mongolia and Japan making a migratory journey to the warmer climes of Australia during late spring and summer.
These birds rarely settle on the ground, preferring to eat on the wing and scoop water when they're thirsty. They're also harbingers of a change in weather. When I saw them, the sky was a clear, cold blue; now, a couple of hours later, it is grey and overcast. It's also bitterly cold, like mid-Winter.
I've never seen these birds here, which was why I was so interested in identifying them. They wheeled and whirled overhead, into a very chilly wind. I suspect they usually stick to the warmer inland areas, but the gale force winds have blown them to the coast.
They've come a long, long way for a summer holiday; shame summer has decided it's staying home this year.