James Norton has revealed he had therapy after being "badly bullied" at boarding school.
"I didn't have the greatest time," he said.
"I was quite badly bullied for five years and I was at boarding school so I couldn't leave. So it's complicated."
The actor, who stars as ex-convict Tommy Lee Royce in the hit crime drama, went on: "I've had a great therapist for the last four years, and it's not from a place of drama.
"I'm luckily not suffering from depression or anything like that but it's been really, really helpful just understanding what that was."
Norton said that in his opinion boarding schools are "really weird places".
"We're the only country who still sends our kids away voluntarily," he said.
"Most countries if you have got some sort of discipline problem or the parents are in the army or whatever then maybe they send them away. But we do it because it's this old-fashioned hangover from the colonial era really."
The star also opened up about missing home, saying "all these young kids are just deeply, deeply homesick and they're just lost".
"For some of them, that pain manifests itself in kind of being needy or rebellious, maybe the class clown," he said.
"But some of them get angry and rather than crying out for their mum they just bully someone."
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