Behind-the-scenes look at the making of Doctor Who. It's the nail-biting finale to series four and the Doctor's arch enemy brings the universe to the brink of extinction. Featuring highlights from the climactic battle in the Crucible and interviews with David Tennant, Billie Piper, Catherine Tate, Freema Agyeman, Russell T Davies, Julie Gardner and Phil Collinson, as they reflect on the highs and lows of the two companions' amazing journey through the series.