IN Terry Gilliam's future-set new film, The Zero Theorem, his anti-hero stares at computer screens and waits to discover the meaning of life.

Back in the here and now, the director and born again Python gazes at his diary and wonders how he can crowbar more hours into the day.

"I've got an opera coming out on June 5, which I've been working on for a year and a half already. Then there's the Python shows in July, then hopefully Quixote at the beginning of September, so I'm running off to Spain looking at locations and casting. Then there's an autobiography that has to come out for Christmas."

At 73, Gilliam is in no more mood to slow down than the Pythons are to book Jim Davidson as their warm up man.

The Yank in the Python pack (though he has long been a fully paid up British citizen) is in Glasgow for the city's film festival premiere of The Zero Theorem. Besides the double Oscar-winning Christoph Waltz playing Qohen, a worker drone of the future, the cast of the fantasy drama also includes Matt Damon and Tilda Swinton. The A-listers, like the crowds due at the 02 Arena in London this summer, still like to come out and play for Gilliam.

He hasn't been in Glasgow for a while and finds the old place changed. "It's completely torn down and rebuilt. It's not so nice. It's lost the heaviness of some of the old buildings that were there. Now it's all glass and steel. It's still a beautiful town, it's probably got some of the most beautiful spires in the UK."

Spoken like a man who wanted to be an architect when he was young, and so it proves. After his first year at college in LA, the Minneapolis-born Gilliam found a summer job with an architects firm. There, he witnessed how designers would dream of beautiful buildings only to be brought back to earth by mundane-minded clients.

"Every film I do is about me playing at being an architect," says Gilliam, "without the problems of a real building."

What astonishing constructions he has overseen over the years, from the Python films and Time Bandits to Brazil, The Fisher King, Twelve Monkeys, and the Imaginarium of Dr Parnassus. Along the way, there has been minor disaster, notably in the collapse of the first attempt at making The Man Who Killed Don Quixote in 1999, and tragedy, as when Heath Ledger died in 2008 during the filming of Dr Parnassus. Ledger was family, says Gilliam, and when the news came through he did not think he could go on with the film.

"I said okay I've had enough s*** dumped on me over the years, I'm worn out, I can't deal with this, I'm going home. And they wouldn't let me do it. They said you've got to fix it."

"They" are the team he has had around him for many years, a crew that now includes Amy, one of his three children. Gilliam thought no single actor could replace Ledger, so he drafted in three - Johnny Depp, Colin Farrell, and Jude Law. All worked for nothing. The "fraternity of actors" came to the rescue. "That's a very rare situation, I hope it never happens again, but I do seem to respond when I'm thrown into the deep end."

With so much on the go this year, he will have to. Besides the opera, Berlioz's Benvenuto Cellini, for ENO, there is the not so small matter of filling the 02 for ten nights. Crazy busy with rehearsals then? Not quite.

"We haven't spent much time together. We had a read through, we then had a press conference and everybody went their separate ways. Eric [Idle] is effectively directing it. It was his idea, he has wanted to do this for years, finally caught us in a moment of despair," laughs Gilliam.

The shows will help to fill a hole in the Python coffers caused by the loss of a court case over royalties for Spamalot. The run is a big ask for Gilliam, not least because the gap caused by the absence of the late Graham Chapman has to be bridged.

"Without Graham we're having to swap things around so I'm ending up doing things that Palin did, which is utterly terrifying because Mike is the funniest Python of all."

The autobiography has been written, but he feels it needs more work. "It was originally going to be a big book of all my art with some written stuff to wrap around it. The art has been pushed aside for 'the story of my life'. Somehow it is chapter after chapter of 'I', 'I', 'I'. It makes me crazy. I seem to be the centre of everything, the world is just a backdrop for me to perform in. I don't like that feeling."

On the evidence of our meeting, he will have plenty of fascinating tales to relate, not least about the making of Braveheart. Mel Gibson, who was being courted by Gilliam to star in A Tale of Two Cities, had originally wanted the Python to direct Braveheart. When Gilliam declined, Gibson took on the role. "I actually thought he did a very good job." How would Gillliam have done it differently? There's another hoot of laughter.

"There are certain cliche things with the English that I thought, come on! It probably wouldn't look quite like Spartacus. And William Wallace's death would have been much more visceral, believe you me!"

I ask the now obligatory question for any visitor to Scotland. "All I'll say," he opines on the matter of Scottish independence, "is if the Scots pull out and if they get rid of health and safety I'll come and live in Scotland."

Otherwise, he'll carry on living in an England he fell in love with long ago and far away, an England of Ealing comedies and ever changing skies, though he acknowledges that when it comes to skies, Scotland beats most other places.

Given his hero in The Zero Theorem is searching for the meaning of life, I wonder what Terry Gilliam thinks that might be.

"The only meaning there is in life is what you give it. Life has no meaning. Life is just this thing that goes on and it is chaos. Well-organised chaos. That's the silly thing about Qohen, he's waiting for someone to tell him the meaning of his life. I just get on with it."

The Zero Theorem opens in cinemas on March 14