You'll have had your arsenic

THE date is September 1960. The scene, the Gateway Theatre. The occasion, the Edinburgh International Festival and a production of a play called Mary Stuart in Scotland. The climactic moment is approaching when David Rizzio, Mary’s secretary, will be murdered, causing Patricia Kneale, in the title role, to faint. It will be the job of a 20-year-old rookie actor called Brigit Forsyth to catch her before she hits the stage.

Except there’s a snag. Forsyth has realised that if she stands up from where she’s sitting, her "unbelievably heavy" velvet dress will not come with her. The hooks have slipped and the skirt has become detached from the bodice. She has the choice of catching Kneale while wearing only suspender belt and stockings - an act known in the trade as upstaging - or staying put and clutching on to her dress. She opts for the latter and her colleague hits the stage.

"I thought it’s either the queen or my skirt," says Forsyth, looking back on her first professional job after she graduated with flying colours from London’s Royal Academy of Dramatic Art. "It was awful. I didn’t catch her and she wasn’t terribly understanding, which I can’t blame her for, because it must have been awful realising you weren’t going to be caught."

Forsyth would play again with the Gateway company that season in My Three Angels and in an Irish play called The Country Boy - she remembers the titles because they were the first things she did - and would return to the International Festival in 1965 as one of the witches in a Traverse Theatre production of Macbeth (which she calls "the unmentionable" because she’s sitting in her dressing room in Poole’s Lighthouse Arts Centre and it would be bad luck to do otherwise).

Aside from that, she has performed in her native city only twice - in Clive Perry’s staging of The Crucible and in Richard Eyre’s staging of Trumpets and Drums - a factor that explains why so few people realise she is Scottish at all.

"I don’t know why nobody notices," says the mother of two who lives in Cheshire and returns occasionally to Scotland to see her two brothers and friends. "I’ve never made any secret of it. I’m terribly proud that I’m Scots. I always mention it and nobody’s picked up on it. I was actually advised to leave Scotland - which is quite extraordinary - but somebody suggested I would get more experience and variety of parts if I went south. I’ll never know if it was true or not, but I suspect it might be because I’ve had such a variety of work."

The other factor for her secret Scottishness is rather more significant. Forsyth is eternally associated with the role of Thelma Chambers (later Ferris) in Whatever Happened to the Likely Lads, a comedy that’s as Geordie as Sting, Viz comic and the Tyne rolled together. "I think they assume I must be a Geordie," says Forsyth. "If Thelma had been Scots, that would have been it. I would have been Scots for life."

It doesn’t matter that she has enjoyed a 45-year career in TV, theatre and radio. It doesn’t matter that she had an equally high profile - and considerably longer - role in five series of Playing the Field with Ricky Tomlinson. People just can’t shake off the memory of a sitcom that ran for two series in 1973 and 1974, with a spin-off movie two years later.

These days her co-star, James Bolam, who was also in the original 1960s series with Rodney Bewes, refuses to talk about the show - an attitude Forsyth has little time for, even if she’s bemused by the way the programme has lodged itself in the collective memory. Like Penelope Keith in The Good Life or John Cleese in Fawlty Towers, the part of Thelma, the sensible girlfriend hoping to settle down with Bob (Bewes), who is ever likely to be led astray by Terry (Bolam), is one that has overshadowed the most successful of careers.

"Whatever Happed to the Likely Lads hit a spot with people and it seems to breed a kind of nostalgia like nothing else," she says. "I would have to be in a soap now for about a year in a bloody good part for it to have the same impact."

Curiously for one so associated with comedy, Forsyth says she was well into her career before she realised she had a gift for it. Certainly, there was little in her unconventional Edinburgh background to propel her in that direction. She grew up with three brothers and a sister in a family where television was banned and singing madrigals together was considered normal. All the children played musical instruments - she plays the cello to this day - and their architect father would compose pieces for them while their artist mother got creative with the mosaics. It sounds delightful but slightly odd.

Entering the acting profession, her performances in serious stage dramas about Mary Stuart and television roles in Play for Today and one of Dr Who’s early Dalek escapades didn’t mark her out as a would-be sitcom star. "I loved doing things like A Streetcar Named Desire," she says. "But I did a couple of funny things on telly and I do seem to come across well in comedy.

"Just before the Likely Lads I did a really heavy psychological drama called Holly, which was way ahead of its time, terrific telly, but I found it very hard to do. When I got Thelma, I remember reading those scripts and laughing out loud and thought it would be lovely to do some comedy."

Forsyth enjoys the range of her profession and is proud to have played everything from bit parts in Coronation Street to Gertrude in Hamlet in 2002 at the West Yorkshire Playhouse (directed by ex-Traverse chief Ian Brown, with Christopher Ecclestone as her son, the doomy Dane). When it comes to keeping her happy, however, it’s comedy that she loves. "Playing Gertrude was terribly exciting and it was a thrilling production, but I was awfully glad when it was over. Everybody died! It does get to you, and if I was in a long tour of a very serious play, I’d find it very depressing."

WHICH BRINGS US to her return to Scotland in Arsenic and Old Lace, the Joseph Kesselring comedy-thriller made famous by the 1942 Frank Capra movie in which Cary Grant played Mortimer Brewster, a theatre critic who discovers his elderly sisters are poisoning their gentlemen callers to cure them of their loneliness. Forsyth and Angela Thorne (To the Manor Born) play the outwardly sweet old dears who are a little too free with their unusually potent elderberry wine.

It’s a gentle comedy with a deliciously dark edge that has played to enthusiastic audiences on its UK tour so far. "It’s such fun," Forsyth says. "And it’s terrific to hear these big laughs."

But for a woman who appeared more than 30 years ago in a show with the nostalgic refrain "ooh, what happened to you/ Whatever happened to me?", how does it feel to be cast as a little old lady? She is only 65, but her profession does have a way of being ruthlessly frank about appearances.

"I’m happy to move on," she says. "But the audience doesn’t want you to because they loved you the way you were. It’s interesting how much people yearn for The Likely Lads, but it’s sometimes quite difficult to deal with. The turning point for me was in about 1993 at the Royal Exchange Theatre in Manchester where I was given the part of a neurotic New York mum. Suddenly I realised I was a grown-up - I was the older girl in the company. It was a shock. ‘Oh I see - I’ve gone into that now.’ It was also terribly exciting, and the parts I have had since have been wonderful - much better than the parts when I was younger.

"I’ve had such an interesting career and I’ve learned so much about other people through playing all those parts. It stops you thinking about your aches and pains because you’re too busy up there doing it. Creativity is my life and it stops you atrophying."

Arsenic and Old Lace, King’s Theatre, Glasgow, tomorrow until Saturday