Siobhan Redmond plays devil's advocate with Doctor Faustus

Redmond is being hard on herself here. On recent form, playing the lead role of warrior queen Gruach in Dunsinane, David Greig's audacious sequel to Macbeth, and as she prepares to play Mephistopheles in the Citizens Theatre's rewiring of Christopher Marlowe's flawed masterpiece, Doctor Faustus, it couldn't be further from the truth.

Even so, Redmond's slightly damning observation of herself speaks volumes about her onstage presence. From starting out in 1980s comic sketch show Alfresco, and her break-out role as Don Henderson's sidekick Lucy McGinty in private eye drama Bulman, Redmond has always retained her striking sense of self, even as she inhabits a role much more than she thinks she does.

This was as much the case in dark TV cop show Between The Lines as it was on stage in the Tron's celebrated adaptation of Janice Galloway's novel The Trick Is To Keep Breathing, or playing the lead in The Prime Of Miss Jean Brodie. It filters into Redmond's off-duty life, as is apparent when she climbs the stairs at the Citizens Theatre after rehearsals, her flame-haired countenance accentuated by her all-black attire.

"It's a sequence of boxes at the moment," Redmond says of Doctor Faustus. "Magical box upon magical box. So we're just working out how many layers of boxes there are. It's a delightful voyage of discovery, and we haven't even started on the magic yet."

Part of the magic she is talking about comes from two new acts written by Colin Teevan to replace some of Marlowe's garbled original. This is a prospect which Redmond clearly relishes.

"It's your two favourite possible things in the world," she says. "It's a phenomenally powerful and wonderful classical play, but with a piece of new writing, which is also intriguing and mysterious, and which is kind of embedded in it like a jewel. One of the lovely things that it does is make Mephistopheles and Faustus a double act, and you get an opportunity to find out various scenarios that may or may not have happened to Mephistopheles in the past, in earlier incarnations, or manifestations if you prefer. Mephistopheles has a back-story. Of course, one of the troubles with demons is you can't necessarily believe everything they tell you, but at the moment I have no reason to believe it isn't true, so you've even more to play with."

As a woman in a role traditionally played by a man, Redmond admits that "I'm beginning to feel the constraints of the wonderfully rich English language, in that we don't seem to have a word which says he and she simultaneously, so we're having to resort to 'it'. But Mephistopheles isn't really an 'it' in the sense of being sexless or neutered. Mephistopheles has had another life, and is both Arthur and Martha."

Doctor Faustus is a co-production between the Citizens and West Yorkshire Playhouse in Leeds, where the production opens this weekend prior to its Glasgow run, and where former Dundee Rep director James Brining is in charge. The play's director, Dominic Hill, was also in charge of Dundee Rep in tandem with Brining. With writer Teevan on board, this new production effectively reunites the team behind Hill's production of Peer Gynt, which similarly ripped into a classic play with new material. This might also be said of Dunsinane, to which Redmond will return following Doctor Faustus to play yet another fiercely intelligent creature.

"What an opportunity," Redmond says, "to have a year where you get to play two extraordinary roles. I mean, it's not normal for a 53-year-old actress to have one great part in a year, but to have two, I feel very lucky. I think I'm actually a bit in love with Dunsinane. I can feel my pupils dilating as I'm talking about it."

Another thing which might have made Redmond's pupils dilate was being awarded an MBE in the New Year's Honours list, an experience she describes as "astonishing ... I'm not labouring under the delusion that either Her Majesty or any member of her government, current or previous, have had their horizons troubled by my artistic endeavours, but somewhere down the years, someone has felt that my work, either deliberately or by accident, has added to the gaiety of the nation, and that's a really delightful thing."

While she talks with some amusement, Redmond seems genuinely touched by the accolade. "I'm very fortunate in that I work more often than I don't," she says, "and, although the work that I do puts a roof over my head, and satisfies me artistically for the most part, it's not particularly high-profile work, and I'm thrilled that you don't have to be doing high-profile work for someone to say, actually, we've enjoyed that. It's just lovely."

Redmond began acting while at university, where the writer in residence was playwright Marcella Evaristi. Evaristi wrote a show for her charges, which was subsequently directed by a young Michael Boyd. Poet and playwright Liz Lochhead went to see the show and, was impressed enough by Redmond to cast her in her show ,True Confessions, the following year. This meant Redmond had an Equity card before she went to drama school.

What was even better was that one of the people who went to see True Confessions was a Granada television producer looking to put together a team for what became Alfresco. Redmond worked alongside Robbie Coltrane, Stephen Fry, Hugh Laurie and Emma Thompson. It was while she was at Granada that Bulman was being cast, and so it went on.

"It just sort of fell on me," she reflects. "I was very lucky, and I knew it wasn't meant to be happening. I knew I was supposed to be starving in a garret, so I've always been lucky when opportunities presented themselves. I remember arriving at Granada and being handed a brown envelope full of money, and I said, 'I haven't done anything yet', and they said, 'no, that's your per diems' (expenses)."

Redmond's early creative relationships continued, with Boyd at the Tron and the RSC, while Lochhead wrote Perfect Days for her in 1998. The play became a West End hit. Redmond has asked Boyd if he will direct her in Samuel Beckett's play, Not I, "before I get too old to remember the lines, and he said yes, so we're hoping to find an opportunity to do that. I'd like to see if I could rise to the challenge, both of dealing with the beautiful language, and the isolation of being onstage alone."

Despite Redmond's willingness to stick her neck out as an actress, she says: "There have been periods when I've felt I've not been creative enough for it. It's not acting that's the problem, but the business of being an actor, which I sometimes find quite overwhelming, and which will surprise anyone who knows how theatrical I am in my personal life. There have been times I've decided I wasn't going to do it any more, but the combination of yet another lovely opportunity presenting itself, and the realisation that I am not fit for anything else, have kept me doing it.

"I never wanted to have children, and I haven't got children. This is what I do with my life. It's more difficult if you have children. It really is, and a lot of actresses find themselves in a different place once they've had children. Many work through it, but it's not easy. Also, there's a certain amount of fallout in my profession, where it's joyful, but it's also quite a daft way to earn a living. So many people get to a certain point in their lives where they decide to do something more sensible.

"I do feel more at home on a stage than I tend to in any of the homes I've lived in. It's a really mysterious alchemical thing that happens between the script, the audience, the production and the actors. There's a really unpredictable thing that happens, and I think I'm quite addicted to that. People who don't do this for a living tend to think it's ... not necessarily a scary thing, but quite a strange thing to do, when, in a way, it's actually quite a safe thing to do. If you just launch yourself at it, and trust the thing, wonderful things can happen, and I think I'm addicted to that."

Doctor Faustus is at West Yorkshire Playhouse, Leeds, until March 16, www.wyp.org.uk; and the Citizens Theatre, Glasgow, from April 5-27, www.citz.co.uk