From having a wee browse through youtube, I stumbled upon a few videos of Doctor Who filming for series 4!
The second one is more interesting, best till last and all that!
David Tennant apparently 'falling over'
A van drives down the street in the dark...
Both were added around 3 or 4 months ago, and I know that someone has mentioned a black van with flashing lights that makes an appearance in 'Partners in Crime', so maybe from that episode?