It's a stone angel, from the superb Dr Who episode, Blink.
Here's another one:
This is a photograph I took of an original stone angel when I went to the Dr Who exhibition at Earl's Court last year.
The model one is poseable, so we could easily arrange it with its arms outstretched in a going-to-get-you kind of way. We pose it like this, though, because if it can't see us then we know it's safe to blink...