Suranne Jones says her and Sophie Rundle bonded while doing lesbian sex scenes.
The 40-year-old actress - who plays land owner Anne Lister in BBC One's "Gentleman Jack" - had serious "chemistry" with the "Bodyguard" actress, so much so they filmed the intimate moments as if "no one else was in the room".
Suranne told The Sun newspaper: "We used the camera to come in on us and find intimate moments, which was really great, because we were able to just play that between us like no one else was in the room.
"By the end me and Sophie were like two nans with a cup of tea. Like, covers off, hanging out and it was great.
"But we needed to get to know each other to be able to do that.
"We had a "chemistry read" first and when Sophie was cast, I knew straight away, "That's my girl".
"Mine and Sophie's chemistry grew as you see it in real time, throughout the eight episodes."
"Gentleman Jack" tells the story of Anne, who returns to Shibden Hall in West Yorkshire after a period of travel, study and social climbing.
Once back home, she engages in a quest to transform her house and business interests, as well as to find herself a wife.
Suranne and Sophie star in the upcoming BBC One show alongside Joe Armstrong, Jessica Baglow, Amelia Bullmore and Rosie Cavaliero.
The former "Coronation Street" star previously admitted show creator Sally Wainwright got intimacy co-ordinator Ita O'Brien on board to help them with saucy scenes.
Suranne said: "One of the great things she brought was an articulacy - we could talk about the scenes.
"She just started talking about body parts and positions in a matter of fact way, which just liberated us all.
"As well as helping us sculpt the sex scenes, the positions, she's also there to provide support to the artists."