Last updated at 12:27

Pictures: Doctor Who official 50th celebration in London

Thousands of Doctor Who fans are at a special three-day event in London to celebrate the show's 50th anniversary.
But this fan goes one step further by coming dressed as a Dalek!
Doctor Who fan dressed as a Dalek
Former Doctors Peter Davison, Sylvester McCoy and Colin Baker take part in a question and answer session.
Peter Davison, Sylvester McCoy and Colin Baker
The first ever Doctor Who episode, An Unearthly Child, was shown on TV on 23 November 1963.
Doctor Who shopping bags
This fan - dressed as the Tardis - poses with two Daleks.
Fan dressed as Tardis poses with Daleks
A special 50th anniversary episode, The Day of the Doctor, is being broadcast on Saturday night at 7:50pm on BBC One. It's also being shown around the world in more than 90 countries!
Cyberman meets a fan
Can you guess which Doctor this fan has come as?
Billy dressed as one of the Doctors
These guys are there too! Doctor Who boss Steven Moffat poses with Jenna Coleman and Matt Smith, who's leaving at the end of the year.
Steven Moffat, Jenna Coleman and Matt Smith
And this brave boy has an even closer encounter with a Dalek!
Fan meets Dalek
Monster masks from the past 50 years are on display.
Doctor Who monster masks
Thousands of Doctor Who fans are at a special three-day event in London to celebrate the show's 50th anniversary, from Friday to Sunday.
Fans pose in front of the 11 Doctors
Fans at the event are coming face-to-face with some Doctor Who characters... There's also a special effects show and a chance to learn how to walk like a monster!
A Silurian with three fans