It was arguably the most devastating parts of Love Actually.

You know the one: when Emma Thompson's character, Karen, realises that her husband (played by Alan Rickman) is having a (fairly poorly hidden) affair with his assistant. And it was particularly heartbreaking to watch Karen burst into tears when she realised that the necklace she had discovered in her husband's coat pocket prior to Christmas was meant for another woman. As it turns out, Emma Thompson drew upon some real life inspiration when it came time to film the scene. The actress told The Telegraph:

"That scene where my character is standing by the bed crying is so well known because it’s something everyone’s been through."

According to the publication, she was referring to her relationship with Kenneth Branagh, whom she fell in love with when they starred as newlyweds in the BBC's Fortunes of War in 1987. The couple tied the knot two years later, going on to star together in  Peter’s Friends, Dead Again, and Much Ado About Nothing.  But things came to an end between them in 1995, when Branagh started an affair with Helena Bonham Carter after they met while filming Mary Shelley's Frankenstein.  Thompson recalled how she was able to channel her heartache into Richard Curtis' rom-com. She added:

“I had my heart very badly broken by Ken. So I knew what it was like to find the necklace that wasn’t meant for me. Well, it wasn’t exactly that, but we’ve all been through it. "I’ve had so much bloody practice at crying in a bedroom, then having to go out and be cheerful, gathering up the pieces of my heart and putting them in a drawer."

The 58-year-old previously told how she didn't have any hard feelings towards Bonham Carter, calling her a "wonderful woman". She said:

"That is... all blood under the bridge. You can’t hold on to anything like that. It’s pointless. I haven’t got the energy for it... Helena and I made our peace years and years ago... she’s a wonderful woman."