I interviewed Terry Gilliam just over a decade ago and the one essential question I should've asked him occurred to me recently: “So, Mr Gilliam - being a film director, is it worth it?"

Because although he's made some remarkable films it always seems to have been done at great cost and pain. With his talent he could have had a nice Steadman/Scarfe type career as a cartoonist and a much easier time of it, living comfortably in Highgate. Is being a film director worth the grief? This documentary gives the answer and it's basically, “Nah, but what are you gonna do?”

Ham & High: Jonathan Pryce and Terry Gilliam in He Dreams of GiantsJonathan Pryce and Terry Gilliam in He Dreams of Giants (Image: Blue Finch Film Releasing)

Fulton and Pepe may not be in Gilliam's league but they have done something remarkable - made a behind the scenes making-of documentary (he most despised genre in all cinema) that is truly, even profoundly, revealing about film making and the artistic process.

And they've done it twice - both documentaries about Terry Gilliam trying to make his dream project The Man Who Killed Don Quixote. In 2002, Lost In La Mancha followed the production collapsing after six days of shooting due to finance problems, the illness of lead actor Jean Rochefort and a torrential downpour. You literally saw Gilliam's dream being washed away before his eyes, and it was crushing. Two decades later, they are back to chronicle a second attempt and this time there is an even crueller ending – he gets to finish it.

When it was finally released in 2019, Quixote was received with indifference or polite attempts to cover up the disappointment. (My one criticism of their film is that Fulton and Pepe end with Gilliam getting a 20-minute standing ovation at Cannes.)

But the box office failure is almost irrelevant: what comes through most clearly is that by the end of the 30-year struggle to make the project, there was no possibility of a happy ending. As Gilliam himself puts it, "This is not a film, it's a medical condition."

The question that hangs over He Dreams of Giants is whether the film should have stayed in Gilliam's head, where it would always be perfect. Whatever their field, every artist is aware that the finished work is never quite as good as the vision that inspired it, but none have as many hurdles between conception and realisation as a film director. But there is something else at work here, a realisation from Gilliam that he has missed his moment. The optimal time for making this had gone. It's a Chronicle of a Disappointment Foretold: not just the director but everyone involved secretly knows it's not going to turn out well but they need to put it out of its misery; it is their noble duty to be the cast and crew that killed The Man Who Killed Don Quixote.

Pepe and Fulton do get inside the film making process and the insane pressures imposed by the lack of time and money but overall, this is much more a portrait of an artist than a Making Of. In his late seventies, Gilliam is acutely aware of his failing abilities, that he doesn't have the energy or the vision of his younger self. We skip back over his career from Python and Brazil to Baron Münchhausen and an interview with Wogan around the time of the latter's fractious release. There is a sense of regret at what he hasn't achieved. Fellini's Eight and a Half is a recurring reference point. For Gilliam it defined what a film director was. Many cite it as a favourite and perhaps its vision of the film director as ringmaster in a circus he can't control has become self-fulfilling for a generation of creative people, a trap they are conditioned to walk straight into.

The cruellest part of He Dreams of Giants is that finishing the film is Gilliam's biggest fear because he won't know what to do next. He probably won't get to make another and since the first version of Quixote fell apart at the start of the century his output has been a shadow of his early career. The young Gilliam had a talent for subversion and rule-breaking that seemed liberating. At the end of his career, all those flights of fantasy seem a trap to contain him. Even being a Creative visionary is a rut to get stuck in. 4/5 stars.

Directed by Keith Fulton and Lou Pepe. Featuring Terry Gilliam, Adam Driver, Jonathan Pryce. Available on Demand from March 29. Running time: 85 mins.