Terry Gilliam: 'I used to think I could will things into existence. Not any more'

He is the Monty Python animator turned film director famed for his manic creativity who reinvented himself again earlier this year with his operatic debut, Berlioz's The Damnation of Faust, partly set in Nazi Germany.

But now Terry Gilliam, 70, is slowing down. Not only does he reveal that he is struggling with his second operatic work at English National Opera (which up until now has been shrouded in secrecy). He also thinks his film career is over.

"I've actually reached the point of not believing I'll ever make a film again," he says. "I am reminded by my wife that I always feel like that. But the great thing about getting older is that your memory goes."

Gilliam and the Monty Python gang, however, remain inescapable 42 years after they first silly-walked on to British television. Later this month a BBC comedy-drama, Holy Flying Circus, will explore the controversy surrounding the Pythons' 1979 religious satire The Life of Brian. A play running at London's Hampstead Theatre, No Naughty Bits, examines the group's 1975 legal battle against censorship by the US television network ABC. Gilliam is interviewed in Martin Scorsese's documenatary about the Beatle George Harrison, which is out on DVD today. And Faust, which garnered some of the best reviews of Gilliam's career, will be broadcast for the first time on television on BBC Four on Friday.

Gilliam still has creative doubts. He says his next opera will also be by Berlioz – Benvenuto Cellini, a 19th-century two-act opera loosely based on the memoirs of a Florentine sculptor, which is so technically difficult it is rarely performed. "There is a discussion going on," he says. "The problem with me is that opera is so far in advance, it would be a year and a bit away. And I can't do that, that's what I've told [ENO artistic director] John Berry. He wants to do something in 2013, but I can't definitely say yes until I know whether I'm shooting a film next year." He says the prospect of directing another opera is "frightening". "I've got all excited about a particular opera, I love the music, but I've been stuck," he says. "I haven't had the epiphany which I had with Faust".

Gilliam has a history of diving into the unknown. Born in Minnesota in 1940, in previous interviews he has described moving to England after becoming disenfranchised from the 1960s US political landscape. Meeting three future Pythons through children's TV series Do Not Adjust Your Set, he became the group's animator whose visuals were a key element in the show's success.

Post-Python he reinvented himself as a film director, taking on unconventional projects like 1981's Time Bandits. The movie was produced by HandMade Films, which Harrison co-founded. Gilliam attended the Scorsese film's gala premiere last week. "I think it did George justice," he says. "I spoke to one person afterwards who said there should have been more comedy in there. That was fair comment because he was so funny."

Gilliam is notably enthusiastic when talking about the former Beatle. His conversational style is scattergun; one minute he seems bored, the next more focused. He is modest about his achievements with Faust, in which he transferred the legend to Germany in the 1930s, taking in Kristallnacht and the concentration camps. The production ends with Faust and Mephistopheles riding off to hell in a motorbike and sidecar.

Gilliam says that when he first started listening to the opera he "hated it, because I didn't know what to do". "I was losing sleep and finally got there once I decided let's go for it. My reaction to much of it was negative. I didn't like the character of Faust, I didn't like that there were all these musical interludes interrupting the narrative. I thought, let's take what everyone knows, Germany in the first half of the 20th century."

He says he still has reservations about the art form. "When it works, opera is extraordinary. It's like bullfighting. But most of them are just crap. Extraordinary sets, amazing singing, but crap. Jonathan Miller's The Elixir of Love just depressed me because it was so good. Then I saw other things and thought, this is horrible. People are spending 90-odd quid to sit in those seats and they're getting a rotten deal. My approach was always, we are doing a show here".

With Benvenuto Cellini he says "it doesn't get done very often so it will stand on its own two feet. "I don't have a clear idea and that's why I'm worried," he continues. "I have detail, but how do you do it? It's stunning, even better than Faust. The plot is silly, it's a comic opera. But it doesn't leave me all the room I need to shape it. The characters say what they say and they do what they do."

Gilliam sounds frustrated by being torn between directing operas for small, appreciative audiences, and winning financing for his filmmaking first love. Movie projects in development include an adaptation of Paul Auster's 1994 novel Mr Vertigo, about an orphan from St Louis (a Hollywood actor is currently reading for the lead). His short film, The Wholly Family, is touring the festival circuit. "I just know I need to get shooting because it's been three years," he says. "Nothing is back on track. Film is difficult to get funding for unless you're doing a huge movie in 3D."

Gilliam's troubled, longstanding attempt to adapt Don Quixote "just needs one more person to come in," he says with a wry smile. "I just want to concentrate on those films," he adds. "I get easily distracted and greedy to do lots of films. Whenever I do that, things fall apart. I used to believe I could will things into existence but now I am older I know it doesn't work that way."

He has been married to Maggie Weston, a costume designer and make-up artist with whom he has three children, for 38 years. Gilliam says she makes him laugh, and keeps him sane, pointing out that his troughs are always inevitably followed by peaks.

So what does he think about the current revival of interest in the Pythons? "I've had no involvement," he says of Holy Flying Circus. "I just met people yesterday who's seen it and they said it's really funny. Some in the group thought it was a bad idea because it's not us. The thought of Python stopping anyone...One of our members was making phone calls. Just stop it. Just stop it."

He still defines himself as a Python, 40 years on. And he remains just as much of a risk-taker. Talking about his foray into opera, he says, slapping the furniture in front of him: "Let's go for it. Jumping off cliffs is much more interesting than jumping off a table."

Terry Gilliam's production of Berlioz's 'The Damnation of Faust' will screen on BBC Four on Friday at 7.30pm

A life in brief

* Terrence Vance Gilliam was born in Minneapolis, on 22 November 1940.

* He graduated with a degree in political science in 1962, moved to New York and became assistant editor of Help! magazine. It was there that he first met John Cleese, while producing the 'fumetti' cartoons (where speech bubbles were laid atop photographs rather than illustrations) that inspired his later animation work in Monty Python.

* He emigrated to the UK in 1967 and soon began working on the children's TV show Do Not Adjust Your Set. There he met Eric Idle, Terry Jones and Michael Palin, and within a year they joined Gilliam, Cleese and Graham Chapman in launching the surrealist comedy programme Monty Python's Flying Circus. The series spawned four movies – including Gilliam's first as a director, Monty Python and the Holy Grail (above).

* Later turning his hand to more serious films, he found great success with two science-fiction thrillers: 1985's Brazil – which he co-wrote with playwright Tom Stoppard – and 1995's Twelve Monkeys, both of which were nominated for two Oscars. His cult reputation was furthered in 1998 with a wild adaptation of Hunter S. Thompson's Fear and Loathing in Las Vegas, starring Johnny Depp.

* Gilliam was less fortunate with The Man Who Killed Don Quixote. Filming began in 2000 but was never completed because of continued setbacks including floods, injuries and funding problems, while in 2008 his lead actor in The Imaginarium of Doctor Parnassus, Heath Ledger, died during filming.

* He made his operatic directing debut this year with Hector Berlioz's The Damnation of Faust. ROB HASTINGS