They’re a weird mob, the presidents and prime ministers making the big decisions. Cate Blanchett, who plays a fictitious but quite recognisable German chancellor in Rumours – very probably the only zombie horror-comedy ever to be set at a G7 summit – is remembering the footage of real G7 meetings watched by the cast as they rehearsed their unlikely roles as world leaders fleeing from undead Neanderthals.

“You’d have these incredibly awkward, horrendous photographs of them sitting in rooms together,” she says. “There was a strange familiarity, but an awkwardness to their connection.”

Hilda Orlmann, the sensibly coiffed host of the summit, inevitably has something of Angela Merkel about her, but the film’s parallels with real life have more to do with an overall dynamic.

“Mostly it’s about power,” says Denis Menochet, who spends much of the film being pushed around in a wheelbarrow as the French president. Whimpering with self-pity, he bears little resemblance to Emmanuel Macron. “It’s about people with power, like kings and queens, almost.”

Twenty-six years since Elizabeth, for which she received her first Oscar nomination, Blanchett herself retains a queenly authority. In a year when she had predicted she would be stepping back from acting to concentrate on producing, she swept into the Venice Film Festival in September as the star of both Alfonso Cuaron’s episodic thriller Disclaimer and Rumours, this wacky satire directed by Canadian eccentric Guy Maddin and his Winnipeg cohort Evan and Galen Johnson.

The force of the fandom gathered to see her walk the red carpet was impressive: a horde of teenage girls struck up a chant of “Cate, Cate!” as Blanchett gave them a regally friendly wave. They were roughly Ariana Grande’s demographic. Blanchett is 55. That doesn’t seem to matter.

Two weeks later, she was at the San Sebastian Film Festival to receive the festival’s Donostia Award for artistic achievement. Two thousand people gathered to watch the tribute, which included footage of George Clooney comparing her to Marlon Brando and Meryl Streep and saying how grateful he was for her friendship. “F---ing George!” she gulped at the end of it, wiping away tears. She wasn’t the only one.

It is this combination of popularity and credibility that she brings to Rumours, a film that would probably not have been made without her. She had always wanted to work with Guy Maddin, she says in San Sebastian, but what spurred her on was a 2017 film he made with the Johnsons for the San Francisco Film Festival called The Green Fog, which was a reconstruction of Hitchcock’s Vertigo using found footage from other films and TV shows shot in San Francisco. There was no dialogue, but the narrative was patched together with these urban snapshots.

“No one else could conceive of that but those three,” she says. “There is an inherent tongue-in-cheek madness and irreverence and technical genius there that I’m in awe of. And I relished being around that, so I wanted to help get this film made, you know, about the G7 leaders who meet, every year, to try and solve the crisis – the crises, rolling crises, ever-growing crises – in the world, but they don’t have the language to do it. To me it’s a little bit like a fever dream of an episode of Scooby Doo.”

The seven leaders are first seen lined up before a German stately home, posing with their flags. There have been some recent thrilling but grisly discoveries of Neanderthal graves in the castle grounds, where bog men have been buried along with their severed genitals; the leaders duly pose over an excavation holding shiny new shovels. They are supposedly gathering to put out a communiqué. They sit in a candle-lit gazebo for a working dinner, making notes. Their jottings seem more like a word-association game than anything to do with policy.

You could hardly expect better from this lot. The American president, inexplicably an Englishman (Charles Dance) keeps falling asleep; his babblings are duly recorded as a contribution to their ultimate statement. The Italian prime minister, Antonio Lamorle (Rolando Ravello), keeps filching snacks to eat later, while British prime minister Cardosa Dewindt (Nikki Amuka-Bird), a Thatcherite, officiously tries to keep the meeting on track.

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Early in proceedings, Canadian prime minister Maxime Laplace (Roy Dupuis) reaches a stage of inebriation where he is lamenting his many lost loves, who include both Dewindt and the European Commission president (Alicia Vikander), who will later show up in the surrounding woods covered in twigs like a forest fairy and hugging a giant brain.

Of course, these important people never imagined that the buried bog men would have been reawakened and want revenge on the living. Their anxieties are stirred only when the waiters supposed to be refilling their wine glasses fail to emerge from the bizarrely livid dusk.

Harsh but fair, one might think. “When you go to Westminster or Canberra or wherever it is, there is kind of a strange boarding-school quality to the environments,” says Blanchett. “They are so hermetically sealed, so far away from the real world and yet they are making important, impactful decisions.”

In Rumours, these are decisions that are simultaneously loaded with gravitas but are not expected to affect anything. “There are no consequences,” says Menochet. “They discover these mummies that have been killed because they didn’t deliver a good harvest. But never, at any time, do these G7 leaders think they will face consequences for failing to deliver.”

“But what I loved,” Blanchett adds, “is that you could say yes, this is a political satire but then the guys have called it Rumours [after] the Fleetwood Mac album, which was put together when there was so much infighting in the band and everyone was sleeping with one another and bickering.” For her part, Hilde presses herself on the Canadian prime minister while they are stumbling through the woods, trying to evade the zombies, with some sexy talk about liaising with the private sector.

“So there’s that quality too, that this is fuelled with regret, and longing and is quite sexually charged,” says Blanchett. As well as being, as she says cheerfully, so “profoundly stupid” that nothing seemed too weird to include.

“When we were reading it and got to the giant brain I was like, ‘Yeah, of course’. It just felt like the most natural thing in the world. They had a giant derrière in one of their films, so I guess they just like big things. Like the Big Pineapple or the Big Merino. Australians are going to love this movie!”

Cate Blanchett’s CV is a cavalcade of films like this, unlikely contenders she made for her own reasons; even the blockbusters, like the Lord of the Rings films, began as personal, quirky choices. It is a constant striving without a fixed goal.

“I don’t think in a creative life, or life in general, that there can be an end point or destination,” she says. “You have to be alive to going on little unseen paths. To be open to surprises, to take off from the track you thought you were on.”

It’s surely that attitude, an enthusiasm for adventure felt even when not so explicitly expressed, that wins over those legions of young fans. “I’m profoundly lucky that I’ve worked with so many extraordinary directors who have given me extraordinary opportunities,” Blanchett says in San Sebastian. “Some have worked, some not. When you get a chance to work with Terrence Malick, you might end up on the cutting-room floor. But that doesn’t mean the experiences weren’t great.”

Rumours opens on December 5.