Emilia Clarke has revealed the details of a prank war with her Me Before You co-star Sam Claflin while they filming last year.

The 29 year old ‘Game of Thrones’ star is currently promoting the new movie, in which she is the co-star alongside fellow British actor Claflin (The Huntsman and The Hunger Games). Apparently, despite the sombre nature of the movie, the set also became the battleground of an escalating prank war.

Emilia Clarke Sam ClaflinSam Claflin and Emilia Clarke at the 'Me Before You' premiere

“I put fish in his socks, but that was just one of them, the fish that we had for lunch,” Clarke told E! News about how bad it got. “I had limited resources. He had just pranked me and I was like, ‘I've got 20 minutes until the end of the day so I have to get this done’.”

Other practical jokes included Claflin hiding in a wardrobe in Clarke’s trailer for 20 minutes before jumping out, and a fart machine in Claflin’s wheelchair.

More: Emilia Clarke provides comic relief in tear-jerker romance ‘Me Before You’ [trailer]

However, they never went too far and they both also had fun together on set. Claflin described going on a walk through a field outside London when they realised they were in danger of being chased by a herd of cows. “We ran and I carried Emilia on my back,” he said.

They were speaking at the red carpet premiere in London on Wednesday night (May 25th). Based on a best-selling novel by Jojo Moyes, Clarke plays a carer, Lou, who looks after Claflin’s wheelchair-bound character Traynor, and the movie also stars Jenna Coleman and Joanna Lumley and is released on June 3rd.

“I watched an edit of it and found myself crying,” she said about the film and people’s reactions to it, adding that she believes she has an “ugly cry face”. “I've got this little chin thing,” Clarke admitted. “Who actually quivers their lower lip? Apparently, I do.”

However, disability rights campaigners have castigated the film as a “disability snuff movie” with its plotline about assisted dying. Clarke defended their portrayal of the characters, saying: “We were very careful with how we wanted to present things. And we are showing a situation, we are not showing an opinion.”

More: Emilia Clarke explains her #FreeTheP campaign for equality in on-screen nudity