If you need someone to tell your secrets to, don't look at Kit Harington.

The Game of Thrones actor, who stars as the beloved Jon Snow on the hit HBO series, was a guest on The Tonight Show Starring Jimmy Fallon on Friday, where he got candid about the select number of "trusted people" who were informed about the Lord Commander's fate before season six premiered -- and the one person he made an exception for.

WATCH: Did Kit Harington Accidentally Spoil Jon Snow's 'GoT' Fate?

Harington hilariously admitted to Fallon that before it was revealed on the fantasy drama, he told a police officer that his character -- SPOILER ALERT! -- came back to life in order to get out of a speeding ticket.

"OK, one policeman knew," the 29-year-old confessed. "There's a story behind it. I was driving back from my parents' house, and I was driving too fast. I was just being a bit naughty. I was going over the speed limit, and I feel the sirens go off behind me and this policeman comes up, pulls me over."

"He said, 'You do realize how fast you were going, and that's a bookable offense?' And he said, 'Look, there's two ways we can do this: You can either follow me back to the police station now and I book you in or you can tell me whether you live in the next series of Game of Thrones.'"

WATCH: Jon Snow's Fate Finally Revealed on 'Game of Thrones'

Harington revealed that he let the police officer in on the truth and was free to drive away without any punishment.

"He says, 'Mmmhmm. On your way, Lord Commander,'" Harington remembered. "'Keep the speed down this far south of the wall.' Isn't that brilliant?"

Harington claims he only confessed the huge secret to three other people: his girlfriend, Rose Leslie, and his mother and father, whom he "told straight away."

"I was good," Harington said about keeping the big reveal hush, even though he clearly made a few mistakes. "When [the writers] told me, they said, 'You can't tell anyone now. He said Dan [D.B. Weiss], David [Benioff], George [R.R.] Martin, a couple of producers at HBO and, now, you know. And you can't tell your mom, you can't tell your dad, you can't tell your brother, you can't tell your friends -- no one.'"

PHOTOS: Kit Harington and Rose Leslie Make Red Carpet Debut as a Couple

In another interview published on Wednesday in Vogue Italia, Harington couldn't stop gushing over Leslie, who starred as Snow's love interest Ygritte in GoT.

"Because the country is beautiful, because the Northern Lights are magical, and because it was there that I fell in love," he said, reflecting on the moment he knew he only had eyes for the red-haired beauty. "If you're already attracted to someone, and then they play your love interest in the show, it becomes very easy to fall in love."

Earlier this year, Harington's co-star, Emilia Clarke, gushed to ET about Harington and Leslie's coupling. Find out why she said their love is "a beautiful thing" in the video below.