Former EastEnders actress Michelle Ryan and comedian Lee Evans will guest star in a special episode of Doctor Who, the BBC has announced.

By Murray Wardrop - 23 January 2009 • 7:00am

Michelle Ryan with David Tennant: The news appears to dispel rumours that the 24-year-old was being lined up to become the Doctor's new assistant CREDIT: Photo: PA

​​Ryan, 24, will play the character Lady Christina de Souza alongside David Tennant in the Easter special entitled Planet of the Dead.

The news appears to dispel rumours that the 24-year-old, best known for her role as Zoe Slater on Albert Square, was being lined up to become the Doctor's new assistant.

It was reported that the London-born actress was in secret talks with the BBC to star opposite new Time Lord Matt Smith.

Ryan said: "I'm a huge fan of Doctor Who and very excited to be joining David Tennant and the Doctor Who team. It is such a fantastic show and I can't wait to get started."

Evans, 44, will also appear in the special episode playing a character called Malcolm, whose life becomes connected to the Doctor's "under extraordinary circumstances", the BBC said.

The pair join Tennant, who continues his role as The Doctor, and Noma Dumezweni, who returns as Captain Erisa Magambo.

The show's executive producer and writer, Russell T Davies, said: "Michelle is one of the most sought after young actors in the country and we are delighted to announce that she will be joining the team.

"As always the script is being kept strictly under wraps however we can reveal that Lady Christina is a woman with a mysterious past who's going to have a huge impact on the Doctor."

Ryan previously auditioned to replace Billy Piper in the part of the Doctor's assistant but lost out to Freema Agyeman, who currently holds the role.

Smith, 26, who takes over the role from David Tennant, was announced as the 11th and youngest Time Lord earlier this month.

Planet of the Dead will be screened on BBC One in Spring 2008 and filming began in Wales this week.

It is the first of four Doctor Who specials which will air in 2009.