Game of Thrones actor Isaac Hempstead Wright on what really happens on set

Isaac Hempstead Wright plays Bran Stark in Game of Thrones. Photo / Getty Images

He plays a leading role in one of the biggest television shows of all time, but Isaac Hempstead Wright, who portrays Bran Stark in HBO's Game of Thrones, says being on set half his life hasn't come without its challenges.

"It's a pretty serious set," the 20-year-old told news.com.au. "There's not a huge amount of time for messing about."

The British actor, who is in Sydney on a promotional trip for Foxtel, said he'd never expected his role as Bran Stark would evolve into such a significant character in the eighth and final series of the global phenomenon.

"With the whole weird visions thing that Bran was having, I always knew there was something weird and unique about him," Hempstead Wright said of his character.

"But nobody told me he would become the three-eyed raven and exactly what that meant. It was really fun going season by season and seeing what was next for him.

"I remember between the break of filming between season 6 and season 7 one of the directors was like, 'You've got some really cool stuff next season'."

Hempstead Wright's character became a pivotal storyline in the current series of Game of Thrones. But after spending much of the past 10 years filming away from his co-stars — including Maisie Williams (Ayra Stark), Kit Harington (Jon Snow) and Emilia Clarke (Daenerys Targaryen) — the final season has been the most exciting yet for the young actor.

"This has been by far my favourite season (to film)," he said.

"There's characters I never ever thought I'd interact with. I never thought I'd be playing opposite Emilia Clarke. That's the character I have loved watching, and seeing this woman taking charge and taking back the throne … and all of a sudden I'm getting to talk to her and interact with her, and I loved that."

But one co-star Hempstead Wright said would often pose as a comical challenge when on set.

"Whenever Conleth Hill (who plays Lord Varys) is in a scene with you, it's a nightmare," he laughed. That's because you have to work really hard not to let him crack you up."

With only three episodes of the series to go, Hempstead Wright is preparing to start a new chapter in his life post Game of Thrones, saying he has no fear of breaking outside the "Bran Stark" mould.

"I'm so grateful for (Bran)," he said. "I know there's a worry about if this (GoT) will define my life, but you just can't really think like that.

"It is quite daunting to think I've probably done the most significant thing in my life already, but at least it was something really brilliant and something people loved. It will obviously follow us around for the rest of our lives, but it's not some awful show we were a part of … It is something people genuinely loved and is a part of history, so to have that following you around is a bit of a privilege."