Heath Ledger's last role before his untimely death last year was in Terry Gilliam's The Imaginarium of Doctor Parnassus. The director tells DONALD CLARKEhow he dealt with the loss of his leading man while shooting and how the inspiration for Ledger's character was Tony Blair

I MEET Terry Gilliam late in the afternoon of October 5th, 2009. How appropriate. On this day, exactly 40 years ago, the BBC broadcast the first ever episode of Monty Python's Flying Circus. Gilliam, an American cartoonist, who provided animations for the show, was, at the time, often regarded as "the sixth Python". He was, that is to say, seen as more of a George Martin than a George Harrison. Yet, as the years progressed, and he forged his reputation as one of Britain's greatest film-makers, the unrepentant surrealist's vital contribution to Python has become ever clearer. Nobody thinks of him as George Martin now.

“Forty years ago?” he says wistfully and casts his head back. “I don’t know where the time went. The other day we were doing this to entertain ourselves and now we’re old people. Now they give us awards. Python’s ability to find young, new audiences amazes me.”

Gilliam, now a creased, but energetic, 67, is in London to promote his characteristically odd film The Imaginarium of Doctor Parnassus. It hardly needs to be said that the picture had a troubled production. After all, trouble is Terry's business. He was so peeved at the studio's grubby treatment of his 1985 dystopic fantasy Brazil, now rightly established as a classic, that he took out an angry advertisement in Varietychastising the suits. His next work, The Adventures of Baron Munchausen, was a financial catastrophe of Lehman Brothers proportions. The Man who Killed Don Quixote, subject of the great documentary Lost in La Mancha, was cancelled after just a few weeks of disaster-laden shooting. Yet he has never quite accepted this notion that disorder dogs his productions.

“My new answer to that is that all those problems were just preparation for this one,” he says. “There’s always a purpose. If I hadn’t been through all that shit I wouldn’t have been able to come out alive from this film. Maybe Nietzsche was right. Whatever doesn’t kill you makes you stronger. Mind you, at my age, whatever doesn’t kill you just makes you more tired.”

The Imaginarium of Doctor Parnassuswas, of course, the film on which Heath Ledger was working at the time of his death. Now featuring additional cameos by Johnny Depp, Colin Farrell and Jude Law, each playing a version of Ledger's character, the picture follows a travelling theatre company, led by a gravelly Christopher Plummer, as they make their peculiar way through a contemporary gothed-up London and onwards to odder times and weirder places.

Along the way, Ledger’s mysterious loner joins their caravan and gets drawn into the doctor’s long dispute with Satan. To add to the madness, Tom Waits plays the Devil as, well, Tom Waits.

“It’s a funny thing,” Gilliam says. “There’s this scene with this dialogue about the death of young princes, and that seems weird now, but that was always in the script.”

That is, indeed, slightly creepy. A particular snatch of dialogue, mourning the premature deaths of idols such as James Dean and Princess Diana, sounds as if it was plucked from an obituary of Heath Ledger. Yet Gilliam maintains it was in the original script.

“Yes and there’s a scene in the monastery in which Christopher says this is ‘a tale of comedy, adventure and a tale of unforeseen death’. He didn’t want to say those words, because that’s just what happened. When that sort of thing occurs you start to believe there’s a movie god somewhere, making the film for us.”

In interviews leading up to the production of the film, Gilliam suggested that the Ledger figure, a swindler and seducer named Tony Shepherd, was inspired, to some small degree, by Tony Blair. I don’t imagine he meant the film as a tribute to the former British prime minister.

“Not exactly. It’s not based on him. It’s inspired by him. That’s a different thing. I was so angry with what he’d dragged us into – becoming America’s poodle, the Iraq catastrophe. He thinks he’s doing good, but he’s creating catastrophe. Tony Shepherd isn’t a bad comment on all that.”

You can also, if you strain hard, see some parallels with Gilliam's life in the opening sections of The Imaginarium of Doctor Parnassus. The picture begins with a young man – who looks eerily like a 27-year-old Terry Gilliam – wandering drunkenly by the Thames and being drawn into Doctor Parnassus's whacky, unconventional troupe. Am I crazy to see this as a version of the director's induction to Monty Python?

“I wouldn’t say that exactly,” he laughs. “You must think what you like. People can believe whatever they want. I just light the touch paper and allow the explosion to blow up in your face. Parnassus is a guy feeling old and not reaching an audience. There’s something there maybe. That’s me in my low months. How do you reach all these kids with their heads in their video games?”

Okay, so the parallels with Gilliam’s life may be unintended, but they still prove useful. Here was this young cartoonist and animator, raised in Minnesota and California, cast adrift in a London that was still (just about) swinging. Suddenly, he’s part of a ground-breaking troupe of posh entertainers.

He has never fully escaped. Just as Paul McCartney is still referred to as “a Beatle”, John Cleese, Terry Jones, Eric Idle, Michael Palin and Gilliam are still described as “Pythons”. Is it easier to stop being an American than to stop being a Python? “Well, you know that I no longer have American citizenship. So I guess that I am no longer an American. But, yes, I am still a Python. I always will be.

“I don’t think we could work together again, because we’re too much like good friends now. It’s weird. It’s been, maybe, 25 years since we last worked together, and people still insist upon talking about it. I did this for maybe 15 years and this is all you want to talk about. Ha, ha!”

I'm sure fans talk to Gilliam about a great deal more than Python. After cutting his teeth on the team's first feature, Monty Python and the Holy Grail,he went on to direct a series of storming, utterly original films that showcased his singular ability to blend comic fantasy with ponderings on mortality and the wretchedness of conformity. With a CV including pictures such as Time Bandits, Braziland 12 Monkeys,Gilliam has earned the right to his own adjective. Gilliamesque is a hard word to define, but most film enthusiasts know what it means.

Yet he still finds it as hard as ever to get financing. He is currently attempting to revive The Man who Killed Don Quixote, but the conversations with moneymen remain frustrating.

“It’s always the same,” he sighs. “They come up and say: ‘I love all your films. I’ve been a fan for years. But I’m not so sure about this one.’ It’s a different guy speaking each time, but they’re always wearing the same suit.”

Still, he has persevered. There are few other directors who have managed to stay so true to their own vision throughout such a long career. I wonder is he able to define Gilliamesque? Is he as big a fan of his own films as the people who won’t give him the money?

“I just can’t look at my films. I want the distance to look at them as an ordinary punter might. I can’t see them as films. People describe them and they sound great and I think: ‘I’d really like to watch a Terry Gilliam film, but I just can’t.’”

There are, it seems, downsides to being Terry Gilliam.

The Imaginarium of Doctor Parnassus

opens next Friday

The departed: death of a star

It's been a decade since Ridley Scottused digital trickery to enable the recently deceased Oliver Reedto complete his performance in Gladiator. Reed was, however, merely playing a supporting role. When Heath Ledgerdied during the making of The Imaginarium of Doctor Parnassus, Terry Gilliam was saddled with a much more serious problem. Ledger was the lead actor and only a third of the picture was in the can.

“I was like: ‘Fuck. It’s over,‘” he says. “I’ll just have to let it die happily. How do you fix that?”

So what changed his mind? “My daughter just beat me up over it. Then the cinematographer, Nicola Pecorini, got on my case as well. ‘You can’t let Heath’s last work go unseen,‘ they said.”

Gilliam's solution was to make use of a visual conceit that already existed in the script. The story involves a magical mirror, beyond which wonders can be encountered. Each time Ledger passes through the mirror he becomes a different actor: either J ohnny Depp, Jude Lawor our own Colin Farrell. "I began to feel that Heath was posthumously directing this," he says. "He stuck us with this insurmountable problem and that propelled us down a new road. It was a gracious gift. I knew he was generous, but I didn't know he was that generous."

As a result of the other actors’ contributions, a relatively modest amount of digital effects were used.

"Yeah. We had to move one scene to the other side of the mirror. We had to drop a few scenes, but I think all that helped the film. I think the film made itself in a way."

Is it very different to how he originally imagined it? "I've given up trying to remember the original vision. Look, in this sort of case you end up in the same destination you were headed, but the town has changed a little. It's still, say, Chicago, but not as you used to know it." DONALD CLARKE