REHEARSALS are under way for a hotly anticipated one-off special of Doctor Who.Scots actor David Tennant will make a return alongside Billie Piper, to celebrate the show's 50th anniversary.

They will join the current Doctor, played by Matt Smith, for the 3D anniversary show.

It will be the first time Tennant has returned to his role as the 10th Doctor, which lasted from 2005 to 2010.

Piper, who played companion Rose Tyler for two series, last appeared in Tennant's final episode The End of Time.

Tinker Tailor Soldier Spy's John Hurt and Gavin and Stacey's Joanna Page also star.

The first episode of the new BBC1 series hit television screens at the weekend.

Doctor Who producer and lead writer Steven Moffat said he is going to great lengths to keep the content of the special programme top secret.

He said: "I make sure I don't get a script, because I will lose it. I forbid people to hand me one. It's on my computer under lock and key."

BBC bosses announced that the Zygons are returning for the 50th anniversary special.

The shape-shifters have only appeared once before, in the Fourth Doctor adventure, Terror of the Zygons.

Dozens of celebrations are planned for the anniversary, including the issuing of a commemorative coin in New Zealand.

caroline.wilson@ eveningtimes.co.uk