SITTING in his Oxfordshire home, the novelist and playwright John Mortimer peers out from behind the pleasant clutter of his desk. There's a comforting pint of Guinness at his elbow, and from the paddock outside, if you strain your ears, you can almost hear the sound of his pigs grunting happily. There is an atmosphere of contentment around him - and yet there's smoke rising from the man.
The problem is this. Mortimer has been asked to consider Jo Strickland, the character at the centre of Lie Down Comic, his play which premieres in Glasgow this week. If it was true to life, he reckons, Strickland should really be dragging on a fag throughout the performance. "She's loosely based on my first wife. And she smoked like a chimney," says Mortimer, conceding in his next wheezy breath that this effect simply cannot be achieved on the Scottish stage, where cigarettes are banned.
It is a situation which is about to be repeated in England, where anti-smoking laws will soon be enacted. "Do you know, I'm so irritated with the ban I've forced myself to smoke?" he announces. "I don't really want to, but now I have to. This ban is absolute rubbish.
"These people don't realise the limits of government. They should run the legal system and see that the drains work. But you're told how to cross the road. And what to eat. For heaven's sake - think of something more important."
The play's themes are serious enough. The cantankerous Strickland (played by Alison Peebles) is already dying when she is befriended by a stand-up comedian (Sandy Nelson). Their relationship, antagonistic at first, becomes mutually sustaining. As ever, the script is etched with its author's trademark dry wit, for at 83 and reliant these days on a wheelchair, Mortimer remains inspiringly free-spirited. When you set that quality alongside his professional pedigree as a lawyer who fought for civil liberties, it is easy to see why he has fallen out with New Labour.
"Look what it's all come to," he chuckles. "We were dancing in the Festival Hall that day when they were elected, a brave new world was coming. And what have they achieved? An illegal war, a smoking ban... Nothing. "
SINCE HE IS NO longer on the guest list for party functions - and the Tories "bring me out in a rash" - these days Mortimer has to make his political views public in his writing. And that is where his most famous literary creation comes in. The next novel in his 30-year Rumpole sequence - The Antisocial Behaviour Of Horace Rumpole - deals with the efforts of his hero to resist an Asbo, a Blairite innovation which makes Mortimer spit. The book's predecessor was entitled Rumpole And The Reign Of Terror, and it's pretty antsy in tone too.
"That one was about giving away all our civil liberties to the terrorists and having trials without juries and imprisonment without trial," rumbles Mortimer. "It put us back behind Magna Carta. The terrorists have won. It's giving it away to them. That makes Rumpole very angry."
For himself Mortimer remains for the most part cheerfully energetic and remorselessly young at heart. "I don't think you change very much over the years," he says. "You are what you are when you were 11. I just don't take any notice of age." His second marriage to Penelope has endured for the better part of 40 years, but as proof of his young man's outlook he still flirts with other women. "Have you got a lover or a husband," he inquired of a woman interviewer recently. "Is he very nice to you?"
"Everyone flirts don't they?" he wonders now. "Naturally, I very much like working with women."
This ever-flowering adolescence burst out most spectacularly in the 1960s, when his work in film and theatre drew many actresses into his circle. At 37, Mortimer had an affair with Wendy Craig, who was married to the journalist and musician Jack Bentley. Craig gave birth to a son, Ross, though at the time nothing was said about the boy's true origins. It was only when Mortimer's "unauthorised" biographer, Graham Lord, outed the relationship that Mortimer heard about his son, who is also a writer.
"It was the one of the most wonderful things that has ever happened to me," says Mortimer. "For that I forgive [Lord] all his rubbish he wrote.
"Ross and I met after Wendy told me about him and he came to see me. You don't quite know what to say to your 42-year-old son. I had a signed picture of Fred Astaire on the wall. Ross asked: 'Do you like Fred Astaire?' I said: 'I love him - you should write the way Fred Astaire dances, do something difficult and make it look very easy.' And he said: 'Yes. I listen to Stacey Kent, who sings Astaire numbers.' I went to my hi-fi and pressed the button. And on the turntable was Stacey Kent.
"We have many more things in common. It's all nature, not nurture. It has nothing to do with upbringing."
Mortimer was born in Hampstead and educated at Harrow school and Oxford University. His father was a successful lawyer, specialising in divorce, and it was expected that John would follow the profession. But soon after graduation in 1942, other skills emerged when he worked at the Crown Film Unit. Selected as a writer by Laurie Lee, he met "everyone" in the British film industry - the Boulting brothers, Noel Coward, David Niven, Peter Ustinov. He wasn't in the least overawed, Mortimer remembers, but he found the environment strange. "There I was, a middle-class public schoolboy, suddenly in this world of trades unions and carpenters. I got called 'comrade' and 'brother' - that's how I got fixed into the Labour Party."
After the war, twin careers as a writer and lawyer ran in tandem. While he enjoyed a level of notoriety as a high-profile QC - defending the publishers of Oz magazine, and later Gay News, from obscenity charges - his big breakthrough as a writer came with the 1957 radio play The Dock Brief, which became a stage hit and a film starring Peter Sellers ("brilliant in his way, but he thought that next week he would be back on the end of the pier"). His most famous stage production, A Voyage Round My Father, also began life as a radio play in 1963, and was revived last year in a triumphant London production starring Derek Jacobi.
It was a courtroom encounter in Singapore that finally convinced him to quit the legal profession, after Mortimer was asked to defend an opposition politician against a libel suit brought by the president. "I arrived in the robing room at the central court with jet lag. A Chinese lady was in charge. She said. 'There you are: Lumpore of the Bayrey'. I thought: 'I can't spend the rest of my professional life being called this.' I gave it up.'"
Since then, writing and performance have sustained him in an idyllic world of work. He has just completed a three-week run at the King's Head, in London's Islington, where he appeared in Mortimer's Miscellany, alongside a changing cast of young actresses, who were engaged to read his favourite poems and literary extracts while he recounted legal anecdotes.
Last week a DVD of the show was filmed and he was delighted that "my daughter Emily, who is a film star" could fly in from New York to take part in it. Mortimer, who occasionally visits Scotland because "my wife shoots things", is chewing over the possibility of bringing the show to the Edinburgh Fringe later in the year.
For now, he can look forward to visiting Glasgow to see his latest stage show premiered in a tight little arts centre, with its pleasant little bar alongside. The perfect environment for a man of Mortimer's stamp. Perfect in all ways but one. That cigarette-free environment just won't feel right. "I mean, women smoking in pubs were so attractive, I always felt."
Lie Down Comic, Oran Mor, Glasgow (0141-357 6225), Thursday until Saturday, 1pm