Immortals now has another draw: Superman. Henry Cavill was once dubbed by Empire as the unluckiest man in Hollywood. He was desperately close to playing Batman, James Bond and Clark Kent (in McG’s aborted version). Then, he finally landed the part of the Last Son of Krypton when 300 director Zack Snyder (another classmate of Tarsem’s) took the megaphone. Though he’s been a regular in TV series The Tudors and worked with Matthew Vaughn (Stardust) and Woody Allen (Whatever Works) on the big screen, Immortals will be the film most people see him in for the first time. Man Of Steel. Abs of steel. The 27-year-old Brit endured a gruelling regime to prepare to play warrior Theseus — up at 4am in pre-production to carve out a killer physique — and continued the work-outs throughout. “It was non-stop brutal.”

Damn if he doesn't look like a movie star though; the sort of bloke you would consider following into a battle. Perhaps it’s breeding: his dad served in the Navy, he was one brother who is ex-Army, another in the Royal Marines, he was going to join up himself, but acting proved a stronger appeal. They mock him for it, of course, “saying that I’m a soft actor who’s never worked a day in his life. That kind of thing. Then they come to the set and see the kind of work I do and change their mind...”

Tarsem describes Rourke, with affection, as a “pain in the ass” and “fucking brilliant”.

Now, not only is he Superman, but here playing a man who is pretty much an original superhero. “Superheroes came from people having difficult times and needing an imaginary hero to fix their problems,” he says. “This is exactly where mythology came from: people going through hardship and having these imaginary heroes who would defeat the big bad guy. I believe the original Superman is him flying around and picking up Hitler and bringing him back to the UN, and it’s the same thing with mythology: some bastard king, who is killing everyone and raping all the women, and then they have this imaginary demi-god hero who goes and fights him and his beastie in a labyrinth... It’s all the same thing, just in a different era.”

The “bastard king” is Mickey Rourke, who isn’t on set when we visit. Tarsem describes him, with affection, as a “pain in the ass” and “fucking brilliant”.

Cavill doesn’t give much away about working with the sometimes prickly Wrestler star. “It was good. Working with all the actors on the show has been an experience in one way or another.” You can call it evasive or polite. “I understand he has a very busy schedule and it’s... he brings something to each character that is unique, I think, that only Mickey can do. So I’m glad he’s been around.”

Just not around much, it seems. Still, looking at the concept art of his scar-faced, sometimes-masked monarch, it’s not hard to imagine he will be a worthy adversary, raising the trapped Titans to fight Zeus (Luke Evans — Tarsem’s casting his Olympus young) and the other gods, who must rely on Theseus’ to save, well, everything. One way or another, it’s about eternity.

'You just have to be who you are'

“The hero,” says Tarsem, “is basically a nobody who, through his deeds, will be known forever. His immortality is thorough his deeds. And then there’s Mickey, who has an Attila the Hun policy: to knock everything up that you can, have many, many children, and 20 generations down, you might recognise your eyes and you’re immortal. And then there are the gods who, by definition, are immortal, but they fight with each other and they can lose that too...”

I do what comes naturally to me. If it stops working and they stop paying me then maybe I’ll start doing some other shit.

Today, the gods are sprayed gold and look like customers of an outré Soho club night. Evans is preparing for god-bothering action, Freida Pinto (seer Phaedra) and Stephen Dorff (the warrior Stavros) are in the art-heavy production offices, both talking fondly of the diminutive Indian director limping around (after busting his calf muscle, dancing at the early wrap party).

“He said, ‘I envisage you as an exotic Virgin Mary’,” says Pinto. “Coming to set every day with Tarsem directing is like having a work out — he’s so charged up.”

“I think he’s a great director,” says Dorff, “An artist in his own right. I’ve liked his other films. I’ve loved his commercials.”

The possessive film credit ‘A Film By’ is often justly resented by writers and crew, but if it’s used here you get the sense it will be justified. This is definitely a film by Tarsem — for good and / or ill.

Back at film school, he realised something. “I was more interested in the physics of things than I was interested in stories — which was the big handicap. Everybody said, ‘He just cares about the picture, he doesn’t care about anything else.’ Well, it’s what moves you!”

He’s off again, talking at top speed of other directors — and friends. “It’s like, Fincher and Spike Jonze get pissed when I say Michael Bay is as much an auteur as all of us put together. It just might not be our cup of shit, but it’s what he does naturally and he loves it. He is true to himself. When we were in school, you could cut your demo to anything that you wanted, so usually you went with Tom Waits or some musician you could never afford. Michael Bay cut his montage to ‘Take My Breath Away’! [by Berlin, from Top Gun]. And it was fucking shit! But it was his thing. You can’t fault him: what he loves is successful. I think you can recognise a Michael Bay film from a trillion miles — I think that’s what an auteur means. So for me when I do my stuff it’s what comes naturally to me. If it stops working and they stop paying me then maybe I’ll start doing some other shit. But right now, I just do what comes naturally to me.” And breathe...

“You just have to be who you are.”