'Game of Thrones' stars Kit Harington and Rose Leslie announce their engagement in British newspaper

— -- After keeping their relationship on the low for so long, "Game of Thrones" stars Kit Harington and Rose Leslie got engaged in a big way.

The couple announced their engagement in today's The Times of London newspaper.

The notice said: "The engagement is announced between Kit, younger son of David and Deborah Harington of Worcestershire, and Rose, middle daughter of Sebastian and Candy Leslie of Aberdeenshire."

Harington's rep declined to make any additional comment to ABC News.

Harington and Leslie aren't the first British actors to make a formal announcement of their engagement in the newspaper. Benedict Cumberbatch did the same thing in The Times when he got engaged to fellow thespian Sophie Hunter in 2014.

For Harington and Leslie, who were first spotted together in public in 2012, the formal announcement comes as something of a surprise. The couple have long guarded their privacy when it comes to their relationship.

Here's a quick recap of their romance:

Lovers on screen

Harington and Leslie were first cast as on-screen lovers on the HBO hit series -- Harington as Jon Snow and Leslie as Ygritte, known for her line, "You know nothing, Jon Snow." Their characters shared a steamy love scene in a cave before Ygritte died tragically in Snow's arms after being shot in the heart with an arrow at the end of season 4.

Seen out together

Fans first began buzzing about a romance when the co-stars were seen out together on a dinner date in 2012.

But Harington always denied the rumors. "All (rumor) and myth," he told Britain's Evening Standard in 2014. "Me and Rose are very, very close and very good friends. And continue to be, actually. She's wonderful. But no, no love affair."

Going public

Finally after four years of rumors, the former co-stars stepped out as a couple at the Olivier Awards in April 2016. Just before making their red carpet appearance together, Harington admitted on Britain's "Jonathan Ross Show" that they actually fell in love while filming in Iceland. "I fell in love in Iceland," Harrngton told host Jonathan Ross. "I fell in love with my co-star."

Moving in together

More recently, Harington revealed that he was living with his lady love.

In a June appearance on "The Late Late Show With James Corden" he said his "other best friend Rose" had moved into his home after another friend moved out after 10 years. "So, I'm very, very happy and it's going well," he said. "She has all sorts of ideas for the house." Nicole Kidman, who was also a guest on the show, then asked Harington if he is was going to marry Leslie. "I just think it's kind of nice if you're going to live together, maybe to at least get engaged," Kidman quipped. "Step by step," Harington replied.