Horror director Neil Marshall is showing footage from his latest film, Doomsday, at Frightfest, the UK's fantasy and horror movie festival, on Thursday.
Earlier this year, Marshall - best known for cult movie Dog Soldiers - showed the BBC News website's Stephen Robb around the futuristic action movie's set.
In the courtyard of a forbidding medieval castle, an enormous armoured gladiator swinging a spear and shield bears down on an unarmed young woman.
Mad Max, Escape from New York are among Marshall's influences
Bloodied stakes rise violently from the ground in the combat arena, while corpses swing from gibbets in the wind, and a ragged crowd on the battlements above bays for blood.
The woman's speed and agility enable her to dodge the gladiator's violent spear thrusts, sparks flying as the point of the weapon strikes the stony castle ground.
She launches a flying kick, connecting hard with the gladiator's head, but he spins round and smashes her with his shield.
Sprawling on the ground, the woman appears doomed as the gladiator rushes toward her.
A cry of "cut" halts the action, and the combatants are suddenly surrounded by a frenzy of activity by dozens of film crew members.
British writer-director Neil Marshall is shooting his ambitious follow-up to hit horror films Dog Soldiers and The Descent.
"It first came about with this idea that I had for these futuristic soldiers encountering a knight in armour on a horse in the woods somewhere," says Marshall.
"I thought that would make a great image for a movie, but under what context could I possibly do that?"
The story, that has taken five years to reach the filming stage, sees Hadrian's Wall rebuilt and Scotland quarantined to contain a deadly virus.
Thirty years into the future the Reaper virus resurfaces in England, leading an elite group of police officers, headed by actress Rhona Mitra, to be sent to Scotland in search of a cure.
They are soon fighting for their lives against the land's two tribes of survivors - car gangs of cannibalistic punks known as "marauders", and a group, led by Malcolm McDowell's Kane, who have reverted to a medieval lifestyle.
The film also stars Bob Hoskins, Adrian Lester and Sean Pertwee.
It is inside the 15th Century-built Blackness Castle, a popular tourist attraction about 18 miles west of Edinburgh, that Mitra is dodging carefully-choreographed spear thrusts.
Before each shot, Marshall and the film's stunt co-ordinators talk the actors through slow-motion rehearsals of the forthcoming action scenes.
The previous day was spent filming wide-shots of the sequence, while today's close-ups allow the use of Mitra's stunt-double for some shots focusing on her opponent.
Marshall has tried to avoid relying on computer-generated effects
It will take more than two days to film a sequence that will last not much more than two minutes on screen.
"The heroes are captured and put in the castle dungeon, and one of them has to face a gladiatorial trial in the arena," says Marshall.
"It's basically an execution, but dragged out for entertainment. Even in medieval-land they like a bit of gratuitous violence."
Marshall's previous works have earned him inclusion in the so-called 'Splat Pack' of film-makers, along with contemporaries such as Hostel director Eli Roth.
And while Marshall stresses that Doomsday is not a horror film, he makes clear that he is not easing up on the gore.
"I can't resist splashing the blood around," he says.
"I'm out to make a hard-hitting, gruesome action movie. When you hit somebody in the head with a mace and chain, it's going to hurt."
Prosthetic make-up designer Paul Hyett, who also worked on The Descent, helped create decapitations, severing of limbs, people being run over by tanks, a head being blown apart, and the roasting alive of one character.
The movie features "real gross-out moments", says Hyett
He also created the make-up for the victims of the Reaper virus.
"Neil said, 'It's got to be as nasty as possible'. We really wanted you to feel that if one of these guys coughed on you, you are dead," explains Hyett.
The fruits of his labour lie in a variety of hideous figures with bloodied, disintegrating flesh, for which Hyett did considerable research into real illnesses including sexually-transmitted infections.
"Now you can find everything on the internet - infections, diseases that people can get," he says.
"It really grossed me out."
With a $30m (£15m) budget - about 10 times the amount allocated to his previous projects - Marshall admits he was initially daunted by the prospect of directing scenes with up to 700 extras.
"I've only ever worked with 20 before," he says.
"And having so many cameras to work with - on the bigger set-ups we've had 10 cameras.
"I've never had 10 cameras. I've never seen 10 cameras before."
The $30m budget is "low by Hollywood standards", says Marshall
But he adds: "We're still battling exactly the same things as we were if we were doing a low-budget film.
"We're trying to do a $100m movie for $30m, instead of trying to do a $30m movie for $3m.
"So we're always pushing the schedule, up against it all the time, and trying to be creative in making things on a budget."
At which point, as if to highlight his point, Marshall is called back to the more urgent business of directing Mitra's battle to avoid a grisly end.
Doomsday is due in cinemas in 2008. Frightfest continues at the Odeon West End in central London until Sunday.