Knightfall premieres Wednesday at 10 p.m. ET on the History Channel

By Michele Corriston
December 06, 2017 01:00 PM
Credit: The History Channel

Game of Thrones fans craving a medieval clash of kings during this long winter off are in luck: The History Channel’s Knightfall, starring Downton Abbey alum Tom Cullen, also features elaborate fight sequences and steamy sex scenes — but as an added bonus, it’s all based on the real quests of the Knights Templar.

(Ironically, Cullen, 32, has been friend with GoT‘s own dark-haired hunk Kit Harington since their London drama school days. As for Harington’s wedding to Rose Leslie, he says with a laugh, “I’ve been invited, but I can’t tell you when it is, I’m afraid. I’m so sorry.”)

The Welsh actor steals every scene he’s in as Landry, the order’s noble leader on a hunt for the Holy Grail — though he’s got his demons, too, grappling with his own religion in a world beset by mystery, betrayal and political machination. Plus, he’s a lustful sinner, breaking his vow of chastity for an affair so scandalous, we couldn’t possibly spoil it before the premiere.

When Knightfall picks up, the Templars are over a decade removed from the Crusades, licking their wounds in Paris after losing the Grail — until duty calls once more.

“I had been reading a lot of scripts and been really frustrated at what I was reading,” Cullen tells PEOPLE of landing the part. “It got me so excited. It’s epic and something that I’ve always dreamt of doing ever since I was a little boy, being a part of something of this scale and this kind of story. And then from a really egotistical point of view, the character terrified me. He’s a classic hero, Landry. He’s so complex. He’s so torn apart. He’s struggling with his faith. He’s a part of this monastic, warrior monk sect, and he’s loyal to his brothers yet he’s having an affair with a woman.”

“It’s something that really scared me as an actor and something I was really hungry to do,” he adds. “So I really pursued it, did about five rounds of auditions, and luckily they were stupid enough to give me the job.”

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Cullen dove into historical research — and hit the gym, gaining about 30 lbs. of muscle for the role.

“I trained for three months before we started shooting, because I wasn’t in very knightly shape,” says Cullen, whose costume includes a suit of armor weighing a whopping 50 lbs. “My body completely transformed. I’m like twice the size that I was before I started shooting. I was actually looking at some pictures of me from like two years ago and I couldn’t recognize myself. I looked so small!”

Knightfall isn’t all action and shirtless scenes, though — it touches on a time that has shaped the world as we know it.

  • For more on Tom Cullen, pick up this week’s issue of PEOPLE, on stands Friday

“The themes of love and betrayal and revenge, all of those great classic themes are swimming all the way through our show, and I think you’d be remiss not to acknowledge the Holy Wars that were fought, even though the show is set 15 years after that, because if anything, history proves itself cyclical, and the actions of those men 800 years ago, we’re still feeling the repercussions of them now,” Cullen says. “So though the show is a really exciting, fun, high-octane journey that you can go on, as a viewer you can kind of reflect on history as a whole.”

Knightfall premieres Wednesday at 10 p.m. ET on the History Channel.