Lesley Manville and Samantha Morton were "nervous of each other" on the set of 'Harlots'.
The two stars - who play Lydia Quigley and Margaret Wells respectively on the BBC Two drama - shared "very few scenes together", but Lesley has recalled the mutual respect between them.
She said: "Lydia Quigley and Margaret Wells have a history and a rivalry.
"Given the whole main thrust of the story is the conflict between Lydia and Margaret, we actually had very few scenes together. But it was a real delight working with her. She is an amazing actress.
"We were both a bit nervous of each other in an unspoken way. We revealed that later on, that we were quite nervous of each other. Because of the respect and all of that.
"I only mention that because I think it added a certain frisson to our scenes together when we played them.
"That less familiarity gave the scenes some real bite, loading them with all of the historic bile between Lydia and Margaret."
In the show, Margaret is the madam of an up-and-coming brothel, while she used to work for ruthless madam Lydia.
The period drama streamed on Hulu for three years after premiering in 2017, but it was cancelled last year and has now been picked up by BBC Two.
Recalling her experiences working with Lesley, Samantha admitted she felt excited and almost "child-like".
She added: "There was an anticipation of working with somebody like her, almost in an exciting child-like way. She is iconic.
"Her body of work and how she maintains that dignity. She's just a legend to me. I've watched her and admired her work for such a long time. It was an honour and a privilege to work alongside her!"
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