It's part of the campaign for a bid to hold the 72nd World Science Fiction Convention in London in August 2014, which, y'know, would also be cool.
The Worldcon is the premier international science fiction event, and awards the prestigious Hugo Awards for achievement in the field of science fiction. 2014 will be the 75th anniversary of the first Worldcon, in New York in 1939, since when the event has been held every year apart from a break during the Second World War. It was last hosted by London in 1965, nearly fifty years ago.Y'know the Hugo awards given out each year? To get a Hugo, you need to be shortlisted by attendees from the most recent and next WorldCon, then win the ballot of the attendees of just that WorldCon. So if you go to a WorldCon, you get to vote on who wins, etc.
Plus, also, a lot of major authors have a habit of turning up. Which is also nice. I'd love to go to a WorldCon (last UK one was before I'd heard of it), and this'd be great. They have an LJ Comm (londonin2014), a Twitter feed and a Facebook page, so you can go find more info &c. But, y'know, regardles, watch the vid, it's really well done, even if it is a bit over reliant on Doctor Who stuff.
On the subject of cool videos, and completely unrelated, have this pixel invasion added bonus:
Both from andrewducker