Leeds writer Kay Mellor said Dr Who actress Billie Piper "blew her away" when she auditioned for the film adaptation of her worldwide hit play A Passionate Woman.
On the final day of filming for the BBC drama yesterday, much of it in Leeds, the award-winning scriptwriter admitted she had initially been "resistant" to using the former pop star.
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But she was won over by the young actress, whose skill in bringing the character of Betty to life was all the more important because she is based on Kay's mother Dinah who died three years ago.
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A Passionate Woman tells the story of a young wife and mother who falls in love with her Polish neighbour in 1950s Leeds, only for her affair to implode 30 years later on her son's wedding day.
Co-director Kay, who grew up in Leeds and was awarded an OBE in June, said: "I didn't go out to get her (Billie).
"She got hold of the script through her agent and read it and absolutely loved it and was desperate to meet us."
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She added: "There was a little bit of resistance really, because of who she is."
She said Billie was shaking when she walked in to her audition, telling her it was because, "I just really want the part".
Kay said: "She read three scenes for us and she blew me away. I thought she was absolutely brilliant."
A shock confession from her mother, while the two of them were washing up, inspired Kay to write the play.
The production, which also stars The Royle Family's Sue Johnston, plus Alun Armstrong and Frances Barber, is being made for the BBC by Mellor's own Rollem Productions company, with Screen Yorkshire investing 250,000, and is being produced by Kay's daughter Yvonne Francas.
Filming has taken place at Studio 81, Kirkstall Road, as well as at locations including the steps of Leeds Town Hall, a house in Chapel Allerton, Hyde Terrace, King's Hall in Ilkley and Roundhay Park.
Piper, who shot to fame in the 1990s as a teenage singer, won rave reviews for her role as Rose Tyler in the revival of BBC sci-fi show Doctor Who.
She has taken time away from acting after having given birth to a son, Winston, last year.
Kay's previous TV hits include Band Of Gold, Fat Friends and Playing The Field.
A Passionate Woman premiered at West Yorkshire Playhouse in 1992 before transferring to the West End and being staged around the world.
Hugo Heppell, executive producer and head of production at Screen Yorkshire, said: "A Passionate Woman will be one of the stand-out productions of 2010, just as Red Riding was of 2009."