BIG-ACTION, swords and sorcery - it's little wonder there are whispers Britannia could fill the gaping hole left by Game of Thrones. But according to its cast, fans (who are eagerly awaiting the eighth and final season of GoT to drop on HBO next year) will soon realise Jez Butterworth's nine-part debut has its "own thing" going on.

"I'm sure it will appeal to a lot of people who enjoy Game of Thrones," Mackenzie Crook says of the Sky Atlantic drama, which is set in 43AD and follows the Roman army as they strive to crush the Celtic heart of Britannia. But while there's going to be the "inevitable comparisons, it pulls no punches", he says: "It shows how brutal and violent life was in those times."

Viewers will be taken to Britannia, a mysterious land led by warrior women and powerful Druids who claim to channel the forces of the underworld. Like never before, Jez (the writer behind Spectre and multi-award-winning plays Jerusalem and The Ferryman) tells the story of the emotional and physical power struggle between the Druids, Celts and Romans.

Loading article content

"It's very true to its period," reasons co-star David Morrissey. "People might come to the show thinking it's something else, like 'Will it be like another show - Game of Thrones - or whatever?' But once you're in there, it's a world on its own and that will take it through."

"It feels very exciting, it feels very alive, and it feels very relevant, weirdly, to the time in which we live," adds Kelly Reilly. "There's not really anything safe about this place, these people. We don't know what's going to happen, anything can happen."

A tale of epic proportions requires epic characters - and Britannia certainly doesn't disappoint.

There's the fearless Aulus Plautius, as portrayed by The Walking Dead's David Morrissey. One of the greatest Generals to have commanded a Roman legion, Aulus has been charged by Emperor Claudius with conquering Britannia. But, as will come apparent, he has his own agenda.

Then there's Kerra, the headstrong daughter of King Pellenor (Ian McDiarmid) and as skilled a warrior as any other member of the Cantii tribe. Played by True Detective actress Kelly Reilly, Kerra has hated the Druids ever since they cast judgement upon her mother, sentencing her to be flayed alive.

Next, The Detectorists' Mackenzie Crook helms the part of Veran, a 10,000-year-old enigma who knows the secrets of both this world and the next. The tribes believe that gives him immense power: he speaks for the gods.

Finally, take note of Harry Potter star Zoe Wanamaker's brilliant portrayal of Antedia, the "angry" Queen of the Regni tribe. Fierce and unforgiving, she has a score to settle after being betrayed in the past.

As anticipated, the show doesn't shy away from lavish costumes either, with David donning armour and a made-up Zoe, whose elaborate outfits took inspiration from the British Museum.

"It's a flight of imagination based on reality," Zoe, 68, says, admitting the most stressful part of the day was being helped out of the costume 'to pee'. "I was originally from America, and when we first came to this country my mother would tell me, ' The British are barbarians, they painted themselves blue'. So I ended up proving her right."

However the biggest transformation of all was Mackenzie, 46, who spent up to five hours a day in the make-up chair. "We managed to get it down to three and a half hours at the end!" he says with a laugh. "I grew to really love it. It was a meditative process and slowly changing in front of the mirror was a getting into character thing. It was uncomfortable, but not unbearable."

"Zoe and I shared a few scenes together," recalls David, 53. "Our characters might not be on equal footing, because I have this massive army behind me, but we're certainly intellectual equals, and something about that meant I really loved playing those scenes with her."

"My favourite bit was the night shoots where the explosions happened!" Zoe declares. "Towards the end, there's an attack on my camp so they had to set off all these explosives. That was great fun to watch them go!"

For Kelly and Mackenzie, it was shooting at the especially-built ritual site 'Amber Palace' that took some beating. "It looks like Stonehenge, and we had 300 extras dancing and playing drums and a smoke machine going under a full moon!" says Kelly, 40. "I was just thinking, 'This thing is touched with some magic'."

Another highlight for her was working with Mackenzie. "He was channelling something playing Veran," she says. "He's extremely powerful for such a slim guy, and he inhabits Veran with this madness and brilliance. He's so inventive."

Of the Amber Palace, Mackenzie remembers finding himself on top of it "with my fear of heights to perform this massive ritual. I just stepped away from myself and said, 'This is quite possibly how it actually was back then'."

All episodes of Britannia will be available on Thursday, January 18, on demand exclusively with Sky Atlantic and NOW TV