The popular actor who plays Samwell Tarly revealed that he fears for his acting career when the programme comes to an end.
Returning for a penultimate series next week, John will reprise his role once more in the first job he undertook since finishing his drama training.
He said: “I think it’s going to be a difficult shift. It would be easier for people who have left the show who had any kind of career or experience before they came onto the show, but I didn’t.
“I went straight from drama training into Game Of Thrones and I’ve never been an actor and not been in Game of Thrones so I’m not going back to anything.
“People who come into the show after doing all sorts of work, it just becomes another job on their CV and then they go back to not being in Game Of Thrones again.”
He added: “I’m going into completely uncharted territory.”
Samwell was last seen in series six reaching the Citadel in Oldtown alongside Gilly and her son where he intends to train as a Maester.
Comparing his character’s academic aspirations to his own acting career, John said: “I came from a working-class background where people just didn’t go into acting, they just found a job near where they lived and went into that.
“In a way when I had that first blossoming of desire to want to do this professionally that was as much a pipe dream for me as the Citadel is for Sam.
“You just think I’d like to do it but there’s no practical path that I can see to do it.”
Game of Thrones returns to HBO on July 16 and will be simulcast in the UK at 2am on Sky Atlantic. Catch up on season one to seven on NOW TV.