By Mark Savage
Entertainment reporter, BBC News
Freema Agyeman has spent the last 12 months immersed in the Doctor Who-niverse, surrounded by blinking lights, blue screens and A-list actors smothered in prosthetic make-up.
The Doctor has had more than 35 companions over the years
Such is the media interest in the science fiction series that the 28-year-old actress is famous before the first episode has even been screened.
But she claims not to be nervous of the critical reaction to her debut as the Doctor's latest assistant.
"I'm very confident in the work we've done," she says a few days before the show's first airing.
"I'm so excited. I keep thinking it's died down and then something new comes along."
Agyeman was relatively unknown when she was picked to succeed Billie Piper in the role of Doctor Who's assistant.
Previously, her highest profile role was as Lola Wise in the now-defunct soap opera Crossroads, but she also had minor roles in The Bill, Prime Suspect and Casualty.
"I was looking down my CV and I was pretty happy - and then this came along," she says, still slightly bewildered at her good fortune.
Agyeman's casting was revealed to the public last July at a press conference where, she says, she turned up in her usual hooded top and was transformed by a squad of make-up artists.
"I always say it was like The Princess Diaries!" she laughs.
Eagle-eyed viewers will have spotted Agyeman in Doctor Who before, playing a minor character who suffered at the hands of the Cybermen.
The actress has to kiss her co-star in the first episode
This time she plays tough, independent Martha Jones, who is revealed to be a cousin of her earlier character.
Agyeman says Jones is less in awe of Doctor Who than her predecessor, Rose Tyler.
"She comes from a big family and she's training as a medical student when she joins the Doctor, so she can stand up for herself," explains the actress.
In real life, however, Agyeman was intimidated by the timelord.
She confesses to being relieved when her first day on set was spent walking alone through corridors and taking notes.
But she soon sparked up a productive relationship with David Tennant, saying: "He's got so much energy, it's really easy to bounce off him."
Agyeman was also impressed by her co-star's ability to reel off long lists of techno-babble during the show.
"None of us could believe that he'd managed to learn it all - and he was saying it so quickly," she laughs.
Not that Agyeman, a self-confessed science fiction fan, was fazed by the tricky dialogue and quirky gadgets she encountered on set.
She grins as she says the infamous sonic screwdriver is "not just a blue torch - it's magic", then cringes with embarrassment as she recalls how she nearly broke it.
"We were rehearsing and David threw the sonic screwdriver to me and it landed on the floor," she says.
"We were both looking at each other like, 'You did it,' but it turned out it was me.
"Luckily it was a rehearsal prop and not the real thing. The BBC would probably have charged me for a replacement!
Agyeman was amazed by the number of fans at the press launch
"But David's always breaking things off the Tardis by mistake," she adds.
The two co-stars seem to have formed a close relationship, and share a (much-publicised) kiss in the first episode of the new series.
Agyeman says Tennant's technique is "as good as you would expect", but she is keen to point out that she is in a happy relationship.
In fact, she will be watching the series premiere with her boyfriend on 31 March, although she reveals he has never seen the show before.
And while Agyeman says she doesn't want to be changed by fame, her partner is a little more excited at the prospect of having a household name for a girlfriend.
"He'll say to me: 'Look, here's a picture of you,' and he's holding up a copy of the Sun," she says.
"It's quite interesting for him to see this side of things, because he's in property.
"I think he gets a lot of kudos from his colleagues."