To call ‘Doomsday’ violent is an understatement

There is no slow build in “Doomsday.”

Geysers of blood, severed limbs and pustule-ravaged faces blanket the opening frames.

Then Rhona Mitra’s machete-wielding babe with the removable, bionic eyeball shows up to wreak her own pickax-to-the-face brand of havoc, decapitating her way through tribes of Thunderdome-ready cannibals.

That’s when things really get moving.

One character is barbecued alive. Medieval knights on horseback pursue post-apocalyptic marauders, and Malcolm McDowell does his best Col. Kurtz a la King Lear. And there’s a marathon car chase led by a 2008 Bentley.

It’s “Mad Max” meets “Escape From New York,” with a dash of Monty Python.

The auteur responsible for all this mayhem is British writer-director Neil Marshall, and even he acknowledges he’s gone a little hog wild.

“Doomsday” cost about $28 million, courtesy of Universal’s genre arm, Rogue Pictures, and Intrepid Pictures – more than three times the combined total of his previous two films.

“It’s pretty dense, isn’t it?” he quips. “With this one, it was like opening the doors and filming in these grand open fields. I think I was really just wallowing in the scale of it.”

“Doomsday,” which opens in theaters today (and was not screened in advance for critics), isn’t what fans might expect of Marshall.

His previous efforts, 2002’s werewolf picture “Dog Soldiers” and 2005’s spelunking nightmare “The Descent,” were praised as tautly written, lo-fi, character-driven horror films.

“Doomsday’s” rigorous shoot took place in Cape Town, South Africa, and Glasgow, Scotland, involving thousands of extras, a series of grand pyrotechnics and complex fight scenes.

After Marshall saw the sleek Aston Martin DBS in “Casino Royale,” he decided he wanted a super-sexy car in his film, too. So the producers ordered three new Bentleys at $150,000 a pop.

One of the Bentleys skidded backward over a 40-foot cliff, miraculously landing in a riverbed on all four wheels, injuring none of the four stuntmen inside.

Earlier that same day, Marshall and his crew had to evacuate a tunnel when a generator caught fire. In the end, the production’s only serious injury was a broken nose.

The inspiration for the script, as Marshall describes it, came from some creative free-thinking.

He spent years traveling along the English-Scottish border, puzzling over Hadrian’s Wall, which the ancient Romans built to keep out Scottish tribes. He often wondered: “What circumstances would exist whereby that wall would be rebuilt?”

Answer: A flesh-eating virus in Scotland that spreads in 2008 like the common cold, prompting England to fortify its border and leave everyone behind the wall to die.

Marshall took that idea and added one of his other preoccupations: The image of futuristic soldiers facing off with a knight on horseback.

But, he asked himself, how could he create that scenario without introducing time travel?

Answer: Twenty-five years after the plague, the virus turns up in London. In a desperate search for a cure, the British send the steely agent Eden Sinclair (Mitra) to confront the survivors and find a cure.

Puzzled again, Marshall wondered: What would survivors have done for 30 years?

Answer: Form a society of punk-rock cannibals in Glasgow, while cultivating a medieval kingdom of “pure-bloods” at Black Ness castle in Edinburgh.

He admits that some of the worlds he created are “so outrageous you’ve got to laugh. I do think it’s going to divide audiences. …

“I just want them to be thrilled and enthralled. I want them to be overwhelmed by the imagery they’ve seen. And go back and see it again.”