The actor, who plays Jon Snow in the popular HBO series, said that he bawled as he and his cast mates sat down for a read through of the final episode of the show.
"We had a read through last week in fact, so I know everything now," he said during an appearance on BBC's "The One Show".
While the final episode will not air until the series comes to an end with the eighth season in 2019, the actor said he could not help but get emotional.
Harington continued, "It's been an institution longer than any other institution I've been in. School, drama school, anything. I get a bit weepy thinking about it. It's going to be a strange year saying goodbye to everyone and having last scenes with this person and that person. Not only you're attached to it, loads of people around the world are attached to it."
The 30-year-old actor said he has been sworn to secrecy.
"(I was told), 'Don't tell them you're filming. Don't take pictures in Belfast. Don't do all of that'.
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