Inside a cavernous sound stage in sweltering heat, a surreal scene is taking place. A band of skinny, shirtless men wearing filthy shorts and bandannas are clambering onto two giant steel turbines. On a command, they begin to pedal. The job of these sorry souls, called Treadmill Rats, is to operate a platform that brings battle vehicles and warriors up to a mountaintop citadel then back down to a desert wasteland.

Milling around nearby are a group of bald youths, also shirtless and wearing combat pants. They are daubed in white paint and marked with a menacing skull tattoo. Called the War Pups, they answer to a masked warlord known as Immortan Joe, who styles himself as a cult leader in the post-apocalyptic future.

While the Treadmill Rats pedal, the War Pups lounge around waiting for their scene. A make-up artist touches up the white paint on one. Another has found a spot in the sun to study a school book.

Watching the action intently on a monitor is George Miller, the acclaimed director who is about to finally finish filming Mad Max: Fury Road at Sydney's Fox Studios.

The former doctor made his name with Mad Max in 1979, then followed up in 1981 with Mad Max 2 (known as The Road Warrior in the US) and Mad Max: Beyond Thunderdome in 1985. While he has had many other successes, including the Oscar-winning Happy Feet, the trilogy about a damaged cop roaming the lawless Australian wasteland remains a cinema landmark.

Still one of the most profitable films ever made, the first instalment launched an unknown Mel Gibson to stardom as Max Rockatansky and influenced countless celluloid versions of the post-apocalyptic future. Out of Miller's vivid imagination came such memorable characters as Toecutter, Goose, the Feral Kid, the Gyro Captain, Master Blaster and Aunt Entity, as well as an inspired range of futuristic vehicles.

And there, on the platform the Treadmill Rats have been lowering, is one of the icons of the series – Max's Interceptor, the black V8 muscle car he drove at turbo-
charged speed in his battered leather jacket with a cattle dog by his side. Despite the heat, Miller is also wearing a black leather jacket as he directs one of the last of 135 gruelling days on the movie.

"I liked being hot from when I was making the first Mad Max," he says, joking that it might be an attempt to raise his metabolism, or just an idiosyncratic security blanket on set.

Miller describes Fury Road as a "wild and operatic" chase movie that is neither a reboot, prequel nor sequel. "It's revisiting the world," he says. "For me, it's revisiting old friends."

Pursued by Immortan Joe's marauding hordes, a one-armed female warrior named Imperator Furiosa, played by Charlize Theron, drives a giant tanker carrying a precious cargo – his five young wives – through the wasteland. Along the way, she gets help from Max, played this time by Tom Hardy.

In its 114 minutes, Fury Road features no less than 300 stunts, all performed for real on set rather than simulated in a studio with digital effects. "Old school", Miller calls it. There are enough crashes, jumps, tumbles and explosions for producer Doug Mitchell to describe the movie as "Mad Max 2 on steroids".

As epic as that sounds, the movie's production has been even more so. Over 12 years, Miller has had to persevere during three major delays, with three actors down to play Max – including Heath Ledger until his tragic death – a switch of continents, three different Hollywood studios and enough financial challenges to sink just about any other movie.

And with up to 10 cameras shooting the action, Fury Road has been assembled from a huge 480 hours of footage. Back in the sound stage, it's time for a shot that has two War Pups reacting to Max's arrival off screen. They are joined by one of Immortan Joe's sons, Corpus Colossus (Quentin Kenihan), in a harness seat.

"Can we ask Jamie to just drop his head a little
bit," Miller says calmly into a microphone. "Crouch down. Not too far forward, Riley. And we're in action. The vehicles arrive. We're watching Max."

Around the corner, production designer Colin Gibson prepares for another shot. Up a ladder, he is painting a slogan on the wall of what looks like a cave: "There's a new world coming … she's already on her way."

This is the mountaintop vault where Immortan Joe keeps The Wives, played by a glamorous group of actresses and models: Rosie Huntington-Whiteley, Abbey Lee Kershaw, Courtney Eaton, Zoe Kravitz and Riley Keough.

Gibson describes the cave as a combined harem, library, crèche and museum for all the flotsam and jetsam of history. "In a world of horror, this is an attempt to keep all the other bits of civilisation you don't worry about anywhere else," he says. "There's music, art, literature, plants."

A short walk away on the busy lot – Angelina Jolie is directing Unbroken and Russell Crowe is shooting The Water Diviner on other sound stages – Mitchell and Gibson show off more
of the dystopian world. Their team
has built 150 metres of tunnels, where Max is held prisoner and treated as a blood donor.

In another corner stands the truck that Furiosa pilots across the desert. Called the War Rig – one of three built for the movie – it looks like a battered dusty petrol tanker with chunks of two other vehicles welded on top, spiked wheels and a fuel-pod trailer.

"For George, this was Stagecoach, this was John Ford," says Gibson in a reference to the classic John Wayne western that takes place on the move. "There may be 10 million stunts happening out there but this is the stage for the drama. The beating heart."

Upstairs in the elegant Metro Theatre in Potts Point, three kilometres away, is an office with a rich history that dates back to some of the famous miniseries Kennedy Miller made in the 1980s. It was the prime minister's office in The Dismissal, a ship's bar in Bodyline, and a prison in The Cowra Breakout. Now it's Mad Max Central. George Miller's office.

With only weeks until Fury Road opens worldwide on May 14, the director is still flat out finishing all the different versions required for a Hollywood blockbuster: subtitled, dubbed, IMAX and various sound and 3D formats.

Beneath three whirring ceiling fans, signs of the movie are everywhere. There are large black models of the War Rig and another vehicle called the Doof Wagon, which urges warriors into battle in the movie with musician Iota playing a flame-throwing guitar. Elsewhere,  some of the ornate steering wheels worshipped by War Boys, grown-up War Pups, hang on a wall, and a pile of movie posters are waiting to be approved.

For much of the production, the office was lined with 3500 storyboard panels that outline what happens shot by shot in Fury Road. "That's how we conceived the film," says Miller.

A genial figure behind glasses, the 70-year-old has long been one of the country's finest filmmakers, telling serious, thoughtful stories in a variety of genres.

Since forming Kennedy Miller with the late Byron Kennedy in the 1970s, George Miller has directed and mostly produced The Dismissal, The Witches of Eastwick, Lorenzo's Oil, Babe: Pig in the City, two Happy Feet films and the Mad Max trilogy. He also produced Babe (which he co-wrote), Bodyline, Vietnam, The Year My Voice Broke, Dead Calm and Bangkok Hilton. And he's done it all while living in Sydney rather than moving full-time to Los Angeles.

The four-time Oscar nominee – he was a winner for Happy Feet – traces his intense imaginative life back to a childhood based around play, without television, as one of four sons of Greek immigrant parents in the Queensland town of Chinchilla.

After studying medicine at the University of NSW with his twin brother John, then working at St Vincent's Hospital in Sydney, Miller was already making short films when he met Kennedy at a University of Melbourne film workshop.

He worked as a locum while they shot Mad Max around Melbourne, with the story influenced by seeing the damage caused by the country's car culture: the "death by autocide" in rural Queensland, and then dealing with the trauma as an emergency doctor.

"Ever since I was a kid, I've basically lived the imaginative life," Miller says. "I'm pretty hard-wired for that now. So these characters you've come up with, they live like imaginary characters in your head."

One of these characters, Max Rockatansky, unexpectedly jumped back to life as Miller crossed a street in Los Angeles in 1998. "Halfway across, this idea popped into my head," he says. "I thought, 'Oh my, that's a Mad Max movie.' By the time I got to the other side of the road, I said, 'There's no way I'm going to go anywhere near that because I've already done three.'

"Two years after that, I was on a plane flying across the Pacific during the night – from Los Angeles to Sydney – and the whole movie played in my head. It was in a rough form and it was very misty but the scenes played.

"By the time I landed, I told everyone, 'I think we're going to make another Mad Max movie.' "

Influenced by a love of silent movies and Alfred Hitchcock's theory about making films so people in other countries do not need to read subtitles, Miller conceived Fury Road as a helter-skelter action movie told largely through visuals rather than words.

After the apocalypse, there are no books, internet or TV, and language has become purely functional. So Max speaks just 41 lines and Furiosa less than 100. "There's very specific language in Fury Road but people don't do it recreationally and they don't think aloud because they're in extremis," Miller says. "They don't have time to think aloud."

The director and his team devised a new dark age. "All the worst-case scenarios we see in the news come to pass all at once. Economic collapse, power-grid collapse, oil wars, water wars and things we just didn't see coming. There's wholesale organ failure of all the things that glue us together. You jump 45 years into the future. All the coastal cities so far as we know have been razed. Great gangs have marauded like locusts across the land. In the centre of a continent like Australia, there's a new dominance hierarchy, where all the resources are controlled."

Immortan Joe controls artesian water from his citadel and trades with other warlords who run Gas Town, which has the fuel, and the Bullet Farm, which has the weapons.

With computer systems wiped out, the wasteland is filled with whatever can be cobbled together from a more robust technological era. "Everything is found objects," says Miller. Everything on screen, including the wardrobe, weapons, vehicles, dialogue and the way the actors behave, was created from these found objects. Two other rules governed what takes place in the movie. "Just because it's after the apocalypse, it doesn't mean people can't make beautiful things. We see that in early man. The palaeolithics did all that wonderful rock art. In refugee camps in the most impoverished parts of the world, they can make beautiful things. And just because it's the wasteland, it doesn't mean people lose their sense of humour. There's a certain rambunctiousness to the world and the story."

As he talks, editor Margaret Sixel – Miller's partner – arrives in the office. When he praises her "massive brain", she jokes that "together we make the complete person".

He chimes in: "If you can imagine the world's biggest Rubik's Cube, that's what Margie had to deal with."

She chips back: "It takes you three months to view all the material, just watching, before you can do anything – it's the bloody digital cameras they can stick everywhere. Then everyone leaves and the poor editor is left in the cutting room. 'See you later, guys. There's 400 hours. Good luck.' "

The movie has a rapid-cutting style that reflects Miller's view that audiences can process information much quicker than years ago. While Mad Max 2 was made up of 1200 shots, Fury Road has more than twice that many at 2750. "Film language – this relatively new language – has evolved that much in 30 years," says Miller.

What keeps him making movies is the same intense curiosity that once drew him to medicine, a fascination with the power of stories and a passion for new filmmaking technology. "It took us 10 years to get the technology to make Babe talk," he says. "The Happy Feet movies came from seeing motion capture and developing it when [cinematographer] Andrew Lesnie came from Lord of the Rings and showed me the first Gollum motion capture."

Doug Mitchell, who joined what is now called Kennedy Miller Mitchell after Mad Max 2 and took over as producer when Byron Kennedy was killed in a helicopter crash in 1983, says the good doctor's genial nature is deceptive. "You've got to be tough," Mitchell says. "George is very gentle and very humorous and very affable but behind that he's a very capable, strong man. You can't lead a company into a filmmaking venture like this without that."

Back when John Howard was still prime minister, Miller planned to shoot Fury Road in and around Broken Hill in western NSW, with Mel Gibson returning as Max. But shortly before filming in 2003, production stalled due to the looming Iraq War, the rising US dollar, insurance issues and problems with the star's deal.

When the movie was eventually revived – with Miller making two Happy Feet movies in the interim – filming was delayed again when heavy rain caused the desert around Broken Hill to bloom in 2009. And it was delayed again when the desert was still too green in 2010 for a start the following year.

After the first delay, Gibson was no longer young enough (and becoming too controversial) to play the role. Miller wanted to replace him with Heath Ledger until his sudden death in 2008. So the role went to Tom Hardy, best known for Inception and The Dark Knight Rises. "In casting sessions, Tom Hardy walked through the door and I just got the same intense vibe that I got when Mel Gibson first walked through the door," Miller says. They both have "an animal-like charisma".

While Beyond Thunderdome was made with Warner Bros, Miller's unhappy experience trying to make the sci-fi movie Contact with the studio meant Fury Road would be made with Universal Pictures, which had great success with Babe. But after the movie stalled for the first time, it went to 20th Century Fox because of its deal with Gibson. When he dropped out, Warner Bros, with a new executive team, took over the movie.

Without Broken Hill, the filmmakers considered deserts in China and Chile but decided to shoot in Namibia in southern Africa, which had a variety of landscapes, a population that spoke English and enough accommodation for a crew that ranged from 1200 to 1700 during the shoot, plus a cast of 55. But it was prohibitively expensive to ship more than 200 vehicles and all those people across the world. "By the time we got to Namibia, the cost and the additional expense of getting there required us to cut back on what we were going to shoot," Mitchell says. They also found themselves fielding flak from Hollywood executives, who were fearful about what else could go wrong so far from home.

While Miller and his crew  wanted to shoot for 150 days, the extra costs meant cutting back to 100 days in the Namibian desert and another 20 days in a South African studio. "The sacrifice was to cut off the start and the end of the film," Mitchell says. "George wisely agreed that was the way to go because at least we could get all the action in the desert, which was what we needed – the essence of the film. We'd find somehow, later on, a way to cope with the problem."

Two units went out to shoot moving vehicles every day – one with Miller directing, the other with stunt co-ordinator and second-unit director Guy Norris at the helm. Along the way, they abandoned plans to shoot the movie in 3D because it was taking too much time, deciding to convert the movie in post-production.

They persevered, making safety a priority as they shot from June to December 2012. From their base in the town of Swakopmund, they had to move a giant tent city six times to shoot in locations that allowed more rugged terrain, canyons and bogs.

Heat was not the only challenge. At times it was so cold the Wives wore overcoats and carried hot water bottles between takes. "I must confess I got massively stressed for a period out there in Africa, where I'd be on the phone at four in the morning to the States," Mitchell says. "There was a lot of noise going on through the film."

Former model Megan Gale, who plays a rifle-toting warrior named Valkyrie, describes the shoot as "completely surreal". "It was just wild," she says. "There were hundreds of guys in character. My first impression
was – everyone says it – it's mad, it's mental, it's just this crazy world that's just full of people who are desperate to survive and are ruthless. It was just a trip to see it on day one."

Gale was so thrilled to be involved that she took on the stunts she could handle safely, including one that involved rolling out of the way of pursuing vehicles after a motorbike crash. "I just had to trust that they would all drive and hit their mark and miss me," she says. "I had to just roll to the left, to the right, to the left, to the right over rocks. That was pretty exhilarating."

Gale says they shot the scene several times for different camera angles and that the expert stunt crew did exactly what they had to do each time. Even working in extreme conditions, Miller still made himself available to discuss dialogue and costumes to help her with the role.

"It was a gruelling shoot," she says. "I came in quite a few months after they'd been there and he was just collected and calm. I never saw him lose his cool, even logistically a lot of things were happening. There's always something that can go wrong, whether it's a car that breaks down or someone's sick or a stunt is not quite working, and he was just so calm."

Miller says shooting stunts "where if it went wrong, it could go horribly wrong" plus the heat, dust and long days in remote locations, were exhausting. "Every day for 120 days was doing heavy-duty action. It was the relentless quality of it that really took its toll."

Security was also an issue, especially with so many actors and the families of crew members who had joined the shoot. A former SAS soldier, John Iles, headed a security team and moonlighted as a warrior named Ace in the movie. "There were a number of burglaries and he was first there," Mitchell says. "John billeted himself near where the Wives were, so if
anything happened, I had an emergency hotline to him to get down and help."

Mitchell takes great pride in completing Fury Road without anyone sustaining serious injuries during filming. "Without patting ourselves on the back, we got through an extensive war in terms of the potential carnage with real vehicles going at speed – massive vehicles – not just one behind the other but in a convoy attacking each other."

If Fury Road is a hit, it will not be the last audiences see of Mad Max. While working on the movie, Miller and co-writer Nico Lathouris came up with two other stories. One was due to be made as a Japanese-style anime but, with a full script written, has been held back as a live-action movie. The other story has been written as a 200-page novella. There are also plans for a Mad Max live-action arena spectacular with producer-director David Atkins.

Clearly as resilient as he is driven, Miller seems calm about what's at stake. A movie made with a budget of $US150 million to $US200 million – and possibly costing more than $US240 million, including government subsidies – will open on the same weekend in every major cinema territory bar Japan and China.

"Our test screenings have gone well," says Miller. "I'm very cautiously hoping for the best but that's not to say that all this effort won't be for naught."

Miller plans some family time – he and Sixel have two sons aged 19 and 14 and he has a 27-year-old daughter, Augusta, with former wife Sandy Gore – but clearly wants to turn more of those ideas that leap to mind crossing roads into movies. "I often say that if I end up in a nursing home staring into the distance, I'll be playing some movie in my head," he says.