Mark Addy Mark Addy

In Game of Thrones' debut, viewers met King Robert Barantheon, a laid-back monarch who seems more interested in wenching and quenching various appetites than in ruling the Seven Kingdoms. On Sunday, the show will give insights into the fat man who sits on the Iron Throne and the cause of much bloodshed to come.

"The thing about Robert is that he's not really a kingly king," Mark Addy, who plays Robert, tells "He's really a guy, a warrior, a soldier who happens to find himself in a position of power. He'd much rather be with the lads. That's his roots, his heritage."

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In his youth, Robert was good-looking and "muscled like a maiden's fantasy," according to George R.R. Martin's novel on which Game of Thrones is based. "Well, in the day he was a handsome, strong, powerful warrior but there's been a lot of water under the bridge since then," Addy says, adding that there was "no extra padding required" for him to play the currently fat and debauched king. 

Sunday's episode "The Kingsroad" will give a look into Robert's past when he talks to Eddard "Ned" Stark (Sean Bean) about how the Targaryens killed Lyanna, who was Ned's sister and Robert's betrothed. We previously saw the friends visit Winterfell's crypt where her remains were buried.

"It's complicated because there is what Robert thinks he knows, which is that she was abducted by Rhaegar Targaryen and raped and murdered," Addy says. "That is the cause of his deep-seated hatred of all things Targaryen, that's why the Targaryens must die. But that's not necessarily the whole story."

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It's that shared loss and growing up together as wards under Jon Arryn that ultimately prompts Robert to turn to Ned when Arryn, the previous Hand of the king, dies. Addy explains: "Being in that position of power, it's very easy to take your eye off the ball and discover that you've actually surrounded yourself with enemies. There's only one man that you can trust and that's Ned. By making him the Hand of the king, you're bringing your best friend into the same danger that you're in."

Check out this promo to get a better idea of some of Robert's enemies:

It's no wonder he needs a steady and loyal fellow like Ned by his side. The problem is that Robert doesn't always have the wisdom to listen to his friend.

"No, he doesn't. I think that's one of his many character flaws," Addy says. "'Ours is the Fury' is the motto of the Baratheons, and sometimes his fury gets in the way of logic and common sense. He's a bit too fond of his own shouting voice to listen to what people are trying to tell him. So he and Ned get frustrated with each other, but a lot of friends do."

Ned is pretty much Robert's only confidant since his wife, Queen Cersei Lannister (Lena Headey), is no comfort at all. That may not necessarily be her fault though, considering the king often chooses to publicly carouse with other ladies, ignoring her. But she may never have stood a chance with Robert in the first place considering her rival for his affections is a ghost.

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"As far as Robert's concenred, Lyanna is irreplaceable," Addy says. "There is no way anyone would come close to being the person that she was. So from Robert's perspective, his marriage to Cersei was a business transaction that took place in order to keep the dynasty going. There were times obviously when they had sex, but it was in order to provide an heir and that's all."

In fact, their relationship is so passionless that there are few significant scenes between the king and queen in the books, which Addy has read. Co-executive producers D.B. Weiss and David Benioff wrote in a new scene for an upcoming episode to give the royal pair a chance to interact and reveal more of their internal conflicts. Cersei confronts Robert about his lack of feelings for her, and although they come to an understanding, it's not a warm or forgiving one.

"They are wonderful... in a horrible way. That's what makes them intriguing," Addy says.

Game of Thrones airs on Sundays at 9/8c on HBO.