She was raised on a deprived council estate in London, the daughter of an Iranian mother and Ghanaian father who divorced when she was young.

Since completing her university degree in drama, she has acquired the typical actor's CV of stints in The Bill and Casualty mixed with shelf-stacking in the video store Blockbusters.

But now the years of struggle should be over. This month, Freema Agyeman will acquire immediate cult status in the eyes of thousands of fans of the newly-revitalised television hit, Doctor Who. The 27-year-old becomes Martha Jones, the first black assistant on board the Tardis in the 44 years since the show began and the successor to Billie Piper's Rose Tyler.

Speaking at the launch yesterday of the third series since the programme returned in 2005, Agyeman said fans were already proving warm and welcoming. "Billie did a tremendous job. I know no one likes change but the nature of the show is change and hopefully fans will be cool with that and give me a chance," she said.

"There are similarities between Martha and Rose. She's not a wallflower and there is a lovely and different relationship with her and the Doctor. It's been an amazing experience."

Agyeman was born in 1979 and grew up on the Woodberry Down estate in Finsbury Park with her older sister, Leila, and younger brother, Domenic. Though her mother, Azar, and her father, Osei, split when she was a child, she is said to be close to her mother and her father lives near by.

After attending Our Lady's Convent, a Catholic comprehensive in Stamford Hill, and the Anna Scher Theatre School, she took up a place to read performing arts and drama at Middlesex University from where she graduated in 2000.

Apart from the seemingly obligatory appearances in The Bill, Casualty and Silent Witness, her biggest role to date was as Lola Wise, a kitchen assistant, in Crossroads when it returned to TV screens in 2003. She was nominated for best newcomer in the British Soap Awards and for sexiest female in the What's On TV magazine awards that year. But it looks likely that it will be Doctor Who that makes her name.

She first appeared in the show in July last year as Adeola, who met a grisly end at the hands of the Cybermen. Doctor Who producers were so impressed by the young actress that they invited her back for a new part, which she understood to be in the Who spinoff, Torchwood.

"My agent got a call saying they wanted me to audition for a regular role in Torchwood, and I was so up for it. So I went for an audition in London," she told Doctor Who magazine.

"But I had to miss the second audition, because I got sick for a week in January. It was really awful. I was so upset. But then they said that they'd reschedule it. And then, just before the third audition, I got a call from my agent. She said, 'All this time, they've been seeing you for the part of the new companion in Doctor Who, not for a regular in Torchwood.' I couldn't believe it."

A who's who of assistants

Dr Who has had 21 female assistants since the first series in 1963. Among the most memorable are:

Susan Foreman, 1963-64

Dr Who's first helper, Carole Ann Ford, played his schoolgirl granddaughter. She claims to have made up the name Tardis herself. Following Dr Who, she appeared in The Great St Trinian's Train Robbery. Now a voice coach in London, she has said: "After Susan, I just got roles as kookie girls. It was a curse."

Zoe Heriot, 1968-69

Wendy Padbury turned down a role in The Prime of Miss Jean Brodie to play Zoe, a teenage genius from Earth's future. Afterwards, she married Ain't Half Hot Mum star Melvyn Hayes. In recent years she worked as an agent in London and now lives in France

Jo Grant, 1971-73

Played by Katy Manning, Jo appeared alongside the third Dr Who, John Pertwee. Jo, an enthusiastic but clumsy trainee secret agent, joins the UNIT after her uncle pulls a few strings.

Mel Bush, 1986-87

Mel, played by Bonnie Langford, was assistant to Colin Baker and then Sylvester McCoy's doctors. Unlike her counterparts, it was never fully explained as to how Mel came to travel with the doctor. Bonnie Langford went on to star in various television shows and musicals, most recently Dancing on Ice.

Rose Tyler, 2005-06

Billie Piper, the former pop singer, began her acting career with the 2005 relaunch of the series playing Rose, a shop assistant who travels with the doctor after he saves her from the Autons. Played alongide Christopher Eccleston in the first series and David Tennant in the second before leaving to work in films.

Source: The Independent March 2007