"My family does April Fools. Her family doesn’t do April Fools," Kit, who plays Jon Snow on GoT, explained on The Jonathan Ross Show.
To try to get his wife-to-be into the spirit of things, the actor decided to hide a severed head in the fridge. Naturally, it didn't go as he'd hoped.
In the video, Rose opens the fridge before screaming and collapsing onto the floor.
"And after that, she was in tears, and I was there going, ‘April Fools.’ It didn’t go down well."
"She pretty much told me that if I did it ever again, that would be it, and I think that’s marriage included," Kit concluded.
Watch the full clip below: