From comedy to the dark side of life, an actor in Peake demand for TV roles

While speaking 10 to the dozen, she consciously filters out anything that might sound contentious or, worse, conceited. It's not a symptom of insidious media training, just good old fashioned good manners.

At 36 – Peake volunteers her age, another thing many actors are reluctant to do – she has over the last decade or so delivered some of British television's most powerful performances.

Myra Hindley in See No Evil, the lead in a lavish TV adaptation of The Secret Diaries of Miss Anne Lister, Elizabeth Lilburne in The Devil's Whore, Juliet Miller in Criminal Justice, Martha Costello in Silk and most ironically of all for a woman who feels uncomfortable talking about her own success, the ultra-confident Veronica in Shameless.

It's a packed TV career that has seen the actor in steady work for a number of years – although she admits to the fear of unemployment that afflicts all in her profession. It's part of the reason why, on a snowy day last month when Peake should have been enjoying her first day off in weeks, she was instead in a studio on the outskirts of Leeds city centre taking part in a photo shoot for the production of Terence Rattigan's The Deep Blue Sea, which comes to West Yorkshire Playhouse in February.

Wearing a brown 1950s-style dress, her stark blonde hair pinned up, Peake looks straight down a camera and manages the feat of at once looking coy, troubled and strong. Conversation is conducted in whispers and whenever there's a break, someone from what appears to be an entourage of 10, rushes to cover her in a blue dressing gown, in the hope of offering at least a little protection against the bitter temperatures.

However, when Peake wanders over to introduce herself she immediately punctures any notion she is one of acting's luvvies. "Hiya," she says, as if greeting an old friend. RADA trained she may be, but while you can take the girl out of Bolton the accent confirms that you'll never take Bolton out of the girl

It turns out the room contains no entourage. Peake's boyfriend accounts for one of the 10, but the others are staff from the West Yorkshire Playhouse there to either help out – or as it transpires simply be near her. Peake has that sort of effect. As she enjoys a cup of tea at the end of the shoot, dressed now in jeans, a woolly jumper and brown boots, it is clear she eschews any trappings of fame. Despite having her pick of roles, she struggles with the idea of being one British television's star names, an actor in much demand by producers desperate to guarantee an audience.

"You never think of it like that," she insists, almost choking on her tea at the thought. "People say it to me and I just go, 'Oh shurrup'. People say you should just look at your CV, but you never do, do you? I was working with a director recently and I remember sitting thinking, 'I'm rubbish, this is no good, she's going to fire me', so I rang my agent and he just said 'What are you on about?'.

"I suppose when I do think about my career, it beggars belief. It's been a funny old journey."

If any of this sounds affected, it isn't. Peake, who recently moved to Salford after years of living in London, has a staggering lack of ego, perhaps largely due to her early experience of trying to break into acting.

"I'm still that dumpy 15-year-old who couldn't get a part in any of the amateur dramatic groups in Bolton. I used to rock up to auditions with a basin haircut, dungarees, big German para boots.

"I was a right mess. People would look at me and go, 'What are we going to cast you as? You can play a man or an old woman'," confesses Peake. "I had a lot of rejection early on."

Yet she never gave up on her childhood dream and eventually she received a yes – an impressive and pretty important yes. After being knocked back for a place studying drama at Manchester Metropolitan University, she heard RADA was going to be auditioning in the city. It meant she didn't have to find the train fare to get to London, just "2.75 for the bus into town". Believing she had a snowball in hell's chance of actually being accepted, Peake went into the audition more relaxed than she had ever been before.

"I didn't need to be nervous, because I was convinced I wasn't going to get in," she says. Much to her surprise, Peake did get in and, on leaving RADA, she was approached by The South Bank Show which wanted to make a documentary about her progression into the acting world. She had already landed the job of playing Twinkle in the Victoria Wood comedy Dinnerladies and as part of the documentary audiences watched footage of her audition. It was a role not only significant because it got her face on TV, but because she met Victoria Wood.

"She told me that if I really wanted to get away from being typecast, then being big and Northern wasn't going to help me. I sort of knew that really, but when I was first auditioning if someone had told me to lose weight or change my image I would have hit the roof," says Peake.

When it was Wood dispensing the advice, Peake listened.

"I didn't want to play a cheeky Northerner for the rest of my life, I wanted to be stretched and see what I could do, that's why you do it," she says. "So I did change my image and it put me in a different bracket."

That decision led to some fantastic roles and has most recently seen her cast as Hester in the Rattigan play that comes to Leeds next month. In The Deep Blue Sea, Peake plays a woman who has left her older husband, a judge, for an exciting and unpredictable younger man. Directed by Sarah Esdaile, who won high praise last year at the Playhouse for her production of Arthur Miller's Death of a Salesman, the director hand-picked Peake for the role.

"I read the play and thought 'Well, this is fantastic, but why me?'," she says. "That's how I work. If I look at something and think I'm not the obvious choice for it, I'll do it. It makes things a challenge for me. Hester is a real emotional construct – it's about the human psyche and all that – so it's back to the dark side for me." It's a place she's been to before. Perhaps most controversially, Peake played the part of Myra Hindley in the 2006 dramatisation of the story of the Moors Murders, See No Evil.

"At the time I knew a lot of actresses who saw the script and said you'd be mad to do it," says Peake. "Even my agent at the time when she was negotiating with the TV company said that this was a big risk for me and I thought, 'Oh – is it?'.

"I just thought it was horrific. She committed really horrific, awful crimes, but it was a fascinating role to play. I wanted to try to understand why this woman did what she did. How she could do it."

Peake admits that she became a little obsessed when it came to researching the part and says that eventually she had to consciously walk away from the role. She also says: "You have to be careful talking about something like that because it was so horrific..." and not for the first time allows the sentence to trail off.

It's the sort of thing an entourage would have jumped in to stop her saying but then, she doesn't have one of those – just a boyfriend who's waiting for her to finish working on a photoshoot on her day off.

The Deep Blue Sea, West Yorkshire Playhouse, Feb 18 to Mar 12.