THE veteran poet and playwright is talking about Tartuffe, her Scots verse translation of seventeenthcentury French farceur Moliere, the artist formerly known as Jean-Baptiste Poquelin's scurrilous satire of conmen on the make. Next week the play receives a major revival at Edinburgh's Royal Lyceum Theatre, where it first caught fire on its debut two decades ago.

"I was 37, " Lochhead recalls in a Lothian Road coffee shop before making her first visit to rehearsals, "and I wrote most of it, this Scots came out of me, mostly, by a pool in Long Beach, California, where I was staying with a friend of mine who was doing a teaching exchange there for a year. We'd been travelling all overAmerica together on a Greyhound bus. We pitched up, she went to her work in this American high school and I went down by the pool and wrote this thing in Scots in this blue-collar town in California, where we didn't even have a car. I wrote bits of it on Greyhound buses, when I had a couple of long trips on my own. We had vouchers to go to Canada and places, so I'd be a long time on these buses, scribbling away, getting a few lines done, just beginning my relationship with Moliere."

The French writer has had a peripatetic relationship with the Scots theatre. Lochhead's Tartuffe took the original by the scruff of the neck and breathed rude new life into a form too often gentrified. The English stage wanted good old-fashioned naughty fun, rather than the two-fingered anti-establishment sentiments Moliere intended.

As auld alliances go, the relationship between Moliere and homegrown writers has been a fecund one. Long before Lochhead, Robert Kemp transformed Ecole de Femmes into Let Wives Tak' Tent, doing likewise with The Miser, which became The Laird O' Grippy. Hector MacMillan, too, made versions of The Hypochondriak and Le Bourgeois Gentilhomme, which he rendered as Noblesse Oblige. Yet, for reasons that perhaps have something to do with Lochhead's own standing as an intelligent populist, and even though she plays down any defining characteristics of the play, Tartuffe is the one that has captured the public imagination the most.

Coming at the time that it did, when theatre in Scotland was slowly seeking to define itself, Lochhead's irreverent Scots pick and mix appeared to throw down the gauntlet. In some vague selfdetermined manner, it seemed, too, to be a show of strength.

Since then, Tartuffe has popped up in repertoire several times, while Lochhead's own shoestring production a decade ago attempted to capture some of the original's rambunctious joie de vivre which Lochhead felt had been lost from subsequent productions. Indeed, if it wasn't for a particularly duff production in Dundee, chances are this current anniversary revival wouldn't be blessed with the personnel involved in it. Director Tony Cownie appeared in that ill-fated Dundee production, and at some point in a post-show postmortem, a plot was hatched for the cast to put together their own effort.

Cownie went on to direct Miseryguts, Lochhead's version of Moliere's The Misanthrope, as well as her version of Chekhov's The Three Sisters. With such creative synergy between the pair, Cownie's take on Tartuffe should have great fun with the play's in-built anarchic spirit.

Today, with popular successes including Perfect Days having played London's west end, and with adaptations of Euripides and Chekhov playing main stages, Lochhead could be said to be something of an elder stateswoman of the theatre. Back in 1986, however, despite the success of her first play, Blood And Ice, and a version of Dracula, she was still best known as a poet who'd been at the vanguard of a wave of writers who'd developed their voices as part of Philip Hobsbaum's writers group at Glasgow University in the 1970s.

In a Glasgow that had yet to become European City of Culture, what Alasdair Gray and future Booker Prize winner James Kelman did in their early novels and short stories, Lochhead, and, equally strikingly, Tom Leonard, did in verse. The demotic they used was both funny and ferocious, and lifted itself off the page and on to the tongue with a ripeness which, in retrospect, was perfect stuff for drama.

"At the time of Tartuffe, " Lochhead recalls, "I'd only been working in the theatre for three or four years, but I'd been working away hard. I was still fresh and new to it all, as I still am. You start from square one all the time, you know. You don't know what you're going to do next. You've got to teach yourself how to do this particular next job, whatever that is. You know, experience doesn't seem to count for very much. It does in the end, but it doesn't feel like it as you go on. It's like life. You keep feeling like a new-born."

As new-born as she may feel revisiting Tartuffe, today Lochhead is wielding the published text of Tartuffe, the introduction of which is filled with underlinings.

"I can't remember whether it was underlined by me, " she says, peering hard at the page, "because I don't do much underlining normally."

She reads: "'The play is also about power.' I've underlined that. I was thinking, it's great whenever you see really great plays: they make you think. You see different things in them because you're older and wiser. The first time I did Tartuffe I was in love with the maid. Now, I'm not in love with, but I relate to, Cleante, the guy who's right."

She laughs at this retrospective comparison. "I now relate to him in that I feel sorry for him in a way that I didn't then. I'm really interested in power games, " she continues. "I'm a dramatist, and it seems to me the really interesting thing about conmen isn't what they do, but how well they pick their mark. It's fantastic, because it's about a conman, and a clever woman tries to play him because of her misplaced self-confidence. I think that's what a lot of comedy's about, isn't it. It's about misplaced confidence."

LOCHHEAD'S OWN CONFIDENCE IS a mix of breezy ebullience, professional charm and brittle vulnerability. As she talks in a rollingly discursive monologue, it's as if she's reacquainting herself with a back catalogue she can barely believe came from her. Sentences are punctuated with accidental question marks, so that, running alongside the pragmatic humility of a craftswoman, there's a constant and infinitely more vital sense of discovery and renewal.

"Tartuffe speaks theatre, " she enthuses. "It gave me the language for Mary Queen Of Scots Got Her Head Chopped Off. It gave me Scots. I didn't know I had it in me. I suppose the difference was that I never had the confidence, and a lot of confidence is about taking something for granted, I think, so it gave me the confidence not to worry about the language."

Of the future: "I don't know if there's another Moliere I'd like to do. There's The Learned Ladies, but I don't know if I can find a context or a concept for it. Let Wives Tak Tent is a lovely prose version of a rhyming play, but the fact that I could rhyme it wouldn't necessarily feel enough of a reason to do it. Because it's about a guardian I'd have to set it in that time, and so I'd have to find a language that felt right for that time.

"For some reason in Tartuffe I didn't change any of their names. But when I was doing Miseryguts I gave them all new names and wrote complete concepts, because it was so easy to translate a letter that somebody had got into a text message, or an accidentally switched on mobile phone. It was fun thinking of those things, but every play needs to be done right. A way in and a context needs to be found. Can we find that again 20 years later? I don't know the answer to that yet. I'm not going to spend a lot of energy feeling scared about it, but it might not work. Given the actors we've got, I'd be very surprised, but who knows?"

Tartuffe, Royal Lyceum Theatre, Edinburgh, January 14February 11.