Shirley Whiteside meets the Scottish actor playing a Dublin crook

At first glance Martin Cahill would probably not be anyone's idea of a notorious, ruthless gangster. He didn't smoke or drink and his hobby was pigeon fancying. With his unremarkable features, Bobby Charlton hair-style, and trainspotter's anorak, Cahill seemed to be just another anonymous face in the crowd in his native Dublin.

The only visible irregularity in his life was his domestic arrangements. Cahill, who signed on the dole, was somehow supporting two families. He was married to and had children with Frances while having a parallel relationship, and fathering children, with her sister Tina. Curiously both women seemed to accept this somewhat unusual notion of an extended family.

Martin Cahill was a clever career criminal who was well-known to the Dublin police. In 1986 he masterminded the robbery of the Beit Collection, stealing 11 Dutch Old Masters from Russborough House in County Wicklow. The haul was conservatively estimated at #30m, at that time the biggest art theft ever. It was the most daring and audacious crime Cahill had attempted and the police, who suspected Cahill was behind the robbery, desperately tried to find the evidence to arrest him.

But for the man also known as ''The General'' this was a crime too far. Years of taunting the police with their inability to pin anything on him and his absolute refusal to kow-tow to the paramilitaries finally caught up with him. Cahill was shot and killed by a hit-and-run gunman in Dublin. The IRA claimed responsibility.

Vicious Circle, written by Kieran Prendiville and showing on BBC 1 tomorrow, is an absorbing thriller based on the story of Cahill's life. Events from more than a decade are compressed into less than two hours and, aside from Cahill and his immediate family, the other characters in the film are fictional.

''At the end of the day I was not writing a documentary,'' says Prendiville, who also wrote the drama series Roughnecks and Ballykissangel. ''This is a work of dramatic fiction based on the life of an extraordinary criminal. The protagonists are like sharks, circling each other endlessly.''

The film features a strong cast of Irish actors in the leading roles, including Andrew Connolly, Gerard McSorley, John Kavanagh, Michael Liebmann, and Michelle Fairley. But director David Blair decided to cast Edinburgh-born actor Ken Stott in the crucial role of Cahill. Blair, also a Scot, had previously worked with Stott on the award-winning drama serials Takin' Over The Asylum and A Mug's Game.

''I wasn't looking for somebody who looked like Cahill,'' says Blair. ''Ken is a great actor but he also has that slight menace and that is important because even though Cahill is not a robust, physical character he has to get that across. In any case, I was quite keen to cast against the obvious.''

''I would probably not have done this if David had not persuaded me to,'' adds Stott. ''I felt Cahill was a peculiarly Dublin character and really ought to be played by somebody from there. But David persuaded me that it was not to do with an accent but with the spirit of a character''.

Stott, one of Scotland's finest actors, gives yet another mesmerising performance as Cahill, a complex and intriguing man. ''What I find interesting about him is that there is a conflict between the villainous behaviour and the tender behaviour,'' says Stott. ''These two things are seemingly at odds but they are quite often prevalent in one character. As an actor that kind of flashpoint is fascinating.''

''Cahill was a kind of Robin Hood figure to those who didn't know him. For those who did know him he was a villain, a dangerous villain. He was in a children's home from the age of 10 and from then on he spent his life either running away from or trying to get back at the authorities. I think he was hell-bent on embarrassing authority and that gave him the most satisfaction.''

though he was a clever man the day came when Cahill pushed his luck a little too far, infuriating the local paramilitaries to the point where he was gunned down in a Dublin street. ''In a way he engineered his own downfall,'' says Stott. ''He risked everything when the better part of his judgement might have told him he was taking things too far.''

Audiences will be seeing a lot of Ken Stott this year. In addition to his starring roles in Vicious Circle and in ITV's police drama series The Vice, Stott has completed two major feature films. He stars alongside Robert Carlyle, Liv Tyler, and Jonny Lee Miller in Plunkette & Macleane, and gives a magnificent performance as an obsessive policeman opposite Billy Connolly in The Debt Collector, writer/director Anthony Nielson's dark and disturbing feature film debut.

This flurry of activity is just reward for Stott, one of those all too rare actors who can breathe life into the characters he plays, making them totally human and utterly believable. The compelling ordinariness of Cahill makes his ruthlessness when crossed all the more frightening.

''There has to be an element of compassion within you for all,'' says Stott. ''We are all Jock Tamson's bairns. That for me is they key to making a character live. If you cannot feel compassion then you are finished.''

n Vicious Circle, 10pm, tomorrow, BBC 1.