Call The Midwife's Jack Ashton has said it can be confusing filming the period drama's love scenes because of his real-life romance with co-star Helen George.
Ashton and George's alter egos on the show, Rev Tom Hereward and Nurse Trixie Franklin, were previously lovers on-screen.
But their relationship crumbled and Ashton's character is now involved with Nurse Gilbert, played by Charlotte Ritchie, on the BBC1 period drama.
Ashton was quizzed on ITV show Lorraine about whether it was difficult remembering who he was meant to be romantically involved with on-screen.
Host Lorraine Kelly asked: "Does it ever get confusing? It must get confusing because your character was engaged to Trixie and then Trixie took to drink and it all went horribly wrong.
"So then, of course, you moved on, which is lovely. But in real true life you're going out with Helen, who plays Trixie."
Ashton said: " I'm now with Nurse Gilbert, Charlotte Ritchie's character.
"Well that's the confusing bit, as long as I remember where I'm going."
Asked when the relationship with George took off, he said: "It blossomed in South Africa, I think, around that time."
He joked: "It's the long hours."
The cast went to South Africa to film scenes which saw the nuns and nurses of Nonnatus House travel to help save an impoverished mission hospital.
Ashton said: "It was great for us as a cast. We got to go away. We all stayed in a hotel. We got to know each other better and when we came back we'd really bonded.
"Let's put some pressure on the writers to move the whole thing to South Africa!"
George, who was previously married to fellow actor Oliver Boot, has appeared on the show since its creation in 2012, while Ashton joined in series three.
The sixth series of the show, based on the memoirs of real-life midwife Jennifer Worth, begins on Sunday.