In preparation for Christmas and the premiere of this year's remaining Doctor Who specials, the BBC's official Doctor Who website launched their online advent calendar for 2009 earlier this month. The advent calendar will feature many exclusive treats over the next four days and door number twenty one on the calendar is now available to open due to the fact that today is the twenty first of December. Behind today's door, there's a new extract from an exclusive interview with David Tennant, Russell T Davies and Julie Gardner. You can view this new video clip here whereas content from behind the calendar's previous doors can be found here. This year's twenty second door on the calendar will be available to open sometime tomorrow and details regarding the next special advent treat will be posted here on this site soon. What do you think of this new interview extract?