http://www.bbc.co.uk/news/uk-23029507 (http://www.bbc.co.uk/news/uk-23029507)
Well, the woman talking about it is clearly batarmadillo insane.
Seems likely that smooth glass plus vibrations from a road on one side and a load of visitors on the other might well make a statue do that if it happened to have the right shape/weight of base etc.
Yeah, that or it's a weeping angel.
If all weeping angels did was move in circles extremely slowly, I don't think they'd be much of an issue for anyone :P
My immediate thought was the shape of the base combined with footfall. Then again, maybe it's the faeries!
Maybe it's some sort of a cellphone from 1800 BC.
It was probably left on vibration mode.
And someone accidentally dialed it. :P
Makes even more sense.
I was actually too tired to be perverted.
Now I feel ashamed.