'The Pandorica Opens' Clip!

A clip of Saturday's episode 'The Pandorica Opens' has been leaked (I'm presuming, as it isn't on any BBC feed or site). It features The Doctor, Amy and River Song discovering quite a lot.
And, yes, it is a HUGE SPOILER. So all spoiler-phobes should look not watch! You have been warned!!

'The Pandorica Opens' is broadcast in the UK Saturday 19th at 6:40PM on BBC One.

What are your thoughts on this clip? What about this episode?
Please comment.