Last updated at 1:07 AM on 23rd January 2009
Michelle Ryan looks set to become the next Doctor Who companion after landing a plum role in the show's Easter special.
The former EastEnders actress will appear in Planet of the Dead, which will be broadcast on BBC1 in April.
She will play Lady Christina de Souza, who accompanies David Tennant's Doctor on a dangerous bus trip.
Co-stars: Michelle Ryan, left, is tipped to be Doctor Who's (played by David Tennant) new assistant in the Easter special
Comedian Lee Evans will also make a cameo appearance.
Executive producer Russell T Davies said: '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.'
Both Tennant and Ryan were spotted filming on location in a bus yesterday.
The Easter special is one of four stand-alone episodes of the show to be broadcast this year. In each, the Doctor will have a different companion.
However, BBC bosses have not yet announced who will star alongside new Doctor Matt Smith in the 2010 series.
Tennant and Ryan filming in a bus on location yesterday
Show insiders said that Miss Ryan, 24, is a key contender to play Mr Smith's assistant.
A source revealed: 'Michelle's been in secret talks with BBC bosses.
'They are likely to announce her as Doctor Who's new assistant very soon.
'She is perfect for the role. She is good looking and the right age to star alongside Matt.
'Everyone agrees they look great together and reckon fans will think they're the perfect team too.'
The source added: 'The BBC launched Michelle's acting career as Zoe Slater in EastEnders and she will be thrilled to be back with them in such a legendary role.
'It's an incredible opportunity for her and even though she's had a lot of success already she is still young and at the start of her career.'
Doctor Who bosses have a habit for re-using characters and even actors.
Freema Agyeman, who took over the assistant role from Billie Piper, initially played the guest character Adeola in an earlier series.
Catherine Tate originally featured in a Doctor Who Christmas special as a guest star, but her performance was such a hit that producers asked her to return for the fourth series.
Miss Ryan unsuccessfully auditioned to replace Miss Piper when she left the programme.
However, it is understood that she has impressed Mr Davies with her work since.
Michelle recently returned from LA, where she played the starring role in TV series Bionic Woman.
But the show flopped and was not commissioned for a second series and the actress - already suffering jibes about her lack of star status and unconvincing American accent - was soon on a plane home.
