Teenage Game of Thrones star Dean-Charles Chapman says watching himself playing a 12-year-old being seduced by his mature wife was "disturbing" and "messed-up".

Chapman plays 12-year-old young King Tommen Baratheon in the HBO medieval drama who has married the conniving and power-hungry Margaery Tyrell played by Natalie Dormer.

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The pair do a very tame sex scene in season five.

Chapman, who was only 16 when filming took place, says it was his first on-screen love scene and Dormer, who is 17 years his senior, was fully professional and helpful.

"It was very disturbing," Chapman told MTV News after he watched the scene.

"Normally when my stuff's on the telly, I don't watch my own bits.

"But this was such a big scene for my character, so I checked it out. I found out about that scene by reading the script, and I was really shocked.

"I didn't think it would have gone down like that on screen. I was nervous to just be pretend marrying Natalie Dormer."

Chapman is still not comfortable with the scene even though it was filmed months ago and he found it hard to watch.

"It's just really weird as a viewer to watch even if I watch it, it's pretty messed up, because Tommen is such a young kid," he said.

"Margaery is like, this fully grown woman, who is really just using Tommen for the power she can get from him."

He said even though he was topless, he was wearing tracksuit pants below the covers but the same could not be said for Dormer.

While the nudity was brief and Dormer briefly exposed her breasts, Chapman said it took a couple of run-throughs for him to totally relaxed with doing his first on-screen love scene.

"When you're there and actually facing Natalie Dormer, it seems to go on for years," he said.

"It's pretty weird. I only had my top off; underneath the quilt I had trackies on and stuff. So that was all good; I was all good. But Natalie I pat her on the back for what she did."