ACTION-packed movie 300 made quite an impact when it was unleashed at cinemas, not least for the exquisitely honed Spartans, led by Gerard Butler's King Leonidas, who dominated the screen.

Seven years on and a new chapter of this epic saga has arrived. It boasts just as much, if not more, blood, brutality and buff flesh as 300.

It's not a sequel as such, given that Leonidas and the majority of his brothers-in-arms died taking their last stand against the invading Persian forces in the first movie.

But Zack Snyder, who co-wrote and directed 300 and returns to co-write and co-produce Rise Of An Empire, felt there were more stories to be told, after the graphic novelist Frank Miller (who'd made a graphic novel of 300 and was an executive producer on the film) got in touch.

"He contacted me and said he was working on an idea about an Athenian General named Themistocles, who led the Greek navy against the Persian army, which was commanded by this amazing woman called Artemisia," recalls 48-year-old Snyder, who directed Dawn Of The Dead, Watchmen and, most recently, the Superman reboot Man Of Steel.

"When he told me it took place during the same three days as [the Battle of] Thermopylae, where Leonidas faced the Persians at the Hot Gates and with an equally significant outcome, I thought, 'Wow, that's very intriguing'.

"The next thing I knew, he sent me an outline and some drawings and I said, 'OK, we're doing this'."

And so the process of creating a second story that runs on parallel tracks to, and intermittently interweaves with 300 began.

After award-winning commercial director Noam Murro was chosen to helm the project, focus turned to casting. Australian actor Sullivan Stapleton, who was recently injured in Bangkok while filming a new series of Sky's Strike Back, was picked to play general Themistocles, part-soldier, part-politician.

"Whereas Leonidas rules Sparta in a very authoritative, military style, Themistocles must be a great speaker to rally all of Greece to fight as one," says the dark-haired 36-year-old. "He knows they may be no match for the Persians but he loves his country and believes in this new idea of democracy."

His formidable adversary is Artemisia (Eva Green), who Murro asserts "is also driven but her brutality is born of vengeance". French actress Green, who came to prominence as Daniel Craig's doomed love interest in Casino Royale, savoured the opportunity to don an array of vampish couture while carrying out unspeakable acts, like kissing the lips of a man she's just decapitated.

"I love playing evil characters, but especially those who are complex and have a reason to behave in such a way, it's always more interesting," says Green, 33. "What I like about her is that she's ballsy and utterly fearless. Her tragic flaw is her obsessive need for revenge."

Although she was able to do some research on the real Artemisia, the character in the film is "quite a bit different", Green notes. "But then a woman commander all those years ago was rather unusual, so she had to have been exceptionally strong," she adds.

The actress threw herself into training, admitting she's "not the most co-ordinated" person. "It was a bit scary in the beginning," she recalls. "Mark [Twight, the trainer who helped get the cast fit for battle in the first film too] would tell me, 'Don't think - do!'"

While fighting with two swords was a big challenge, Green says the stunt team on the film were "the best ever. It was so much fun. I felt like I was living my dream."

Although no stranger to stunt work, Stapleton shares his co-star's enthusiasm: "I'd never done sword-training before and it's always rewarding to learn something new, especially when you're working with the best of the best."

But perhaps the most daunting task fell to the actors who had to appear on screen as if no time had passed, like Rodrigo Santoro, who reprises his role as Xerxes, the God-King. The process to look the part "was as intense as the first one - hours and hours in the gym and weeks and weeks without ice cream or chocolate".

"But that's the price you pay to be a God-King," adds the Brazilian star, grinning.

In 300, audiences only saw Xerxes in his resplendent god-like state. This time, his transformation's played out on screen, and Santoro enjoyed the opportunity to explore Xerxes' roots.

"We get to see him as a young man and understand how he transformed himself into this splendid being," he says. "The way I see it, it was an act of courage on Xerxes' part, because he had to commit himself to a kind of death before he could experience this rebirth."

As royally bedecked as Xerxes was in the first movie, Santoro and the film-makers agreed they wanted to step things up this time round, and used contact lenses to give him eyes that were blazed but soulless. A desire to up the ante was an objective all departments shared, particularly the visual effects team.

As with 300, almost all of the sets, both interior and exterior, were achieved post-production - but this time, there was the added challenge of battles being waged at sea.

"Our goal was to come up with something that lent itself to the film's hyper-stylised world, so we didn't want the water to be too realistic," says visual effects supervisor Bryan Hirota.

"Once we established the look, there was a lot of very advanced simulation work to implement it. It was a huge technical challenge."

He, along with the hundreds of other crew members, hopes the result is something that captures the essence of the first movie, but offers an added level of drama and action.

As Murro, the man charged with steering this new chapter, says: "I remember before I had heard anything about 300, I was sitting in the cinema and suddenly the trailer came up. I'd never seen anything like it, and then I looked around and other people were having the same reaction. Now, hopefully we can create that sense again."

EXTRA TIME - BRINGING THE FILM TO LIFE

Director Noam Murro wanted the Persians to feel like a dark force, so production designer Patrick Tatopoulos used black as the predominant colour: "Nothing is overly ornate; it is very monolithic."

While the main bodies of water in the film were created by a visual effects team, scenes in which actors enter the water were shot in tanks at studios in Leavesden, Hertfordshire.

Like 300, the amount of blood yielded is extreme and involved meticulous attention in post-production to ensure it matched every blow, cut and slash.

This time, the actors weren't assembled in a training camp before filming began, but trainer Mark Twight set regimes. He credits Andrew Pleavin (who plays Daxos) for "the biggest transformation in the shortest time frame".

Costume designer Alexandra Byrne had the most fun creating costumes to capture the two sides of Eva Green's Artemisia: "The first time she meets Themistocles [to seduce him], she's alluring in a flowing metallic dress. When they meet again, she's all warrior, brandishing two swords and with armoured spikes running down the back of her dress."

300: Rise Of An Empire is released on Friday, March 7.