THOUSANDS of Doctor Who fans will be hiding behind their sofas, or cinema seats, across Scotland and the rest of the UK for the eagerly awaited Day of the Doctor - the sci-fi show's much-hyped 50th anniversary episode.

Steven Moffat, the programme's producer who hails from Greenock, Inverclyde, described the 80-minute edition starring 'three' incarnations of the Time Lord as a huge treat for fans of all ages.

It reunites David Tennant and current doctor, Matt Smith, who are joined by John Hurt as a former incarnation. It is also being shown simultaneously in 3D in selected cinemas.

The enduring popularity of Doctor Who continues unabated and the next actor to step into the Time Lord's shoes will be another Scot, Peter Capaldi, who takes up the baton from Smith next year. However, the current incumbent has said nothing can prepare the Scot for the job. Smith bows out at Christmas and will be replaced by The Thick Of It star next year.

He said: "I don't think anything can prepare you for the experience of what being the Doctor in Doctor Who is but I think he's as ready as he can be. I've just said 'Have a good time, mate'. He'll be great - Peter will hit the ground running and keep flying."

Thousands of 'Whovians' descended on east London yesterday for a three-day celebration of the show ahead of its 50th anniversary. Dozens of doctors - in fancy dress from every era - rubbed shoulders with tinfoil cybermen, daleks and endless aliens. Around 24,000 people are expected through the doors of the Excel centre in east London over the weekend for the Official 50th Celebration.

Mike Green, from Bedford, who came dressed as Tennant's 10th doctor, said: "It's taken a long time to get the outfit right and I wouldn't like to say what it cost but I'm on my fifth suit."

The 29-year-old said: "There is a great social scene and you meet up with friends who dress up as well and meet new people. It's a real community."

Wendy Taylor, 50, from Harwich in Essex, said she was not "a really big fan" but had dressed as a dalek anyway. She said: "This is perfect because everyone looks at the costume and not at me."