Need help identifying a piece of music.

[Timmyb]

This question has come up on another non-music forum and it's starting to annoy me now.
I thought it might be Vaughan Williams but don't recognise it.Certainly sounds British anyway.
I've no doubt somebody here will know what it is.
It's the piece that starts at 4.56 in this video.
Thanks.
http://www.youtube.com/watch?v=Z7iQ4u3OX3Q