Jodie Whittaker on playing a Doctor… in BBC1 drama Trust Me

Her character, Cath Hardacre, is skilled and dedicated but finds herself suspended after blowing the whistle on her colleagues. Suddenly she decides to take the identity of a doctor friend of hers (who conveniently emigrates to New Zealand) and try and wing it.

The drama, written by medic Dan Sefton, focuses on Cath’s strenuous efforts to keep her secret while working in an A&E department of an Edinburgh hospital. She can do basic procedures seamlessly – but will she be able to keep up the pretence when more complicated cases arrive?

Rather intriguingly, Whittaker, whose own mum was a nurse, said at the press launch for Trust Me (which took place before her Doctor Who role was revealed) that she would personally have found the challenge an impossible one. Her reason? “I'm a crap secret-keeper so there would be no way I could put myself in that position.”

For a woman who (as RadioTimes.com revealed last week) had kept the secret about her Doctor Who casting for months, it is hard not to think she was indulging in a little private joke.

But the fact that Cath Hardacre is herself playing a role was, she says, a help for her.

“My character could be out of her depth or like a fish out of water in a lot of her scenes – so in a way that's really helpful. In a weird way, it’s the easiest of performances when you're playing a Doctor and your character doesn't know how to do it. People playing the real Doctors have to seem immediately competent."

She adds: “I enjoy the adrenaline of being on set, because I’m quite good at choreography, I respond well to being taught something physically. That’s why I was terrible at school because they talk you through things rather than physically show you.

“But the thing I struggled the most with, and I think it just comes from basically failing half my GCSE's and never doing O-Levels, is the pronunciation of medicine, even just as a simple word. I mean, call it 'Bob!' or something but it’s not, it’s called something ridiculous but you've got to pronounce it and remember it.

“I love the fact that [Cath's] choices are quite morally dubious and they certainly aren’t black and white. She makes decisions that are quite challenging to justify, even though we know her reasons. I’ve never acted in anything medical before, so it felt completely new. All the physical stuff I could do, all the emotional stuff I was kind of 'been there before', I've played a few emotional characters.”

She’s not wrong there.

Whittaker is probably best known for her portrayal of Beth Latimer, the grieving mother of murdered youngster Danny in Broadchurch. It was where she impressed viewers with the depth and emotional maturity of her acting. Broadchurch creator Chris Chibnall has described her as a "super-smart force of nature" and nabbed her to play the first lead of his Doctor Who tenure.

She also impressed her colleagues on Trust Me who praised her work ethic and good humour – all good signs for when when she takes on the notoriously huge demands of filming Doctor Who for a good chunk of the year.

The long Trust Me shoot also gave Whittaker a certain confidence in her medical skills.

“I did five weeks of studio filming, back to back – all the medical stuff was contained so everything started to become a bit like second nature."

But how would she fare if she were called upon to perform a medical procedure? Would she be able to wing it?

“The writer, Dan, who is also medical consultant and a doctor outside of TV production, showed us a load of stuff that he used when he was training people. He brought in the CPR dummy and showed us how to do a cannula and he, very bravely, let me put a cannula in his vein. I did it right, thank God.

“I feel if there were a real scenario I would at least know how to take it all out of the wrapper and what angle it’s supposed to be and what is supposed to go where. Any kind of diagnosis I would steer well clear of."