You know how it is... you're standing at the sink, doing the dishes after lunch with your mother, and she suddenly starts telling you how she had a passionate affair with the neighbour when you were little, and that he was the only man she'd ever truly loved?
No? Me neither. But this jaw-dropping conversation is what inspired veteran screenwriter Kay Mellor's dramatic story, A Passionate Woman, of a 1950s housewife who, as she describes it, "lost herself to this man. It was the only time I ever heard my mother use the word love about a man."
They say it's always the quiet ones, and thus it proved in this case - as Mellor remembers: "It was so unlikely. She never spent any money on herself, never had her nails or her hair done, she was a woman's woman.
"I looked at her, and she was crying, which I'd never seen before. For 30 years, she'd never told anyone, she'd just grieved for him completely privately."
Sue Johnston and Alun Armstrong in A Passionate Woman
Mellor's mother, played as a young lady on screen by Billie Piper (and later on by Sue Johnston), and her lover were parted in dramatic, tragic circumstances, only partly altered for the screen, and her mother decanted her passion instead into children... which meant that, on her son's wedding day, she went into an unusual decline. This is delightfully depicted on screen by Sue Johnston climbing onto the roof for some sort of emotional sit-in, again not too far from reality as Mellor recalls it:
"When my brother Philip got married, she was distraught, she said she just wanted to just crawl away and die. In the film, I had him moving away to Australia to make it more likely, in actual fact, he only moved around the corner.
"I would say my mother's heart was too big for her environment, and perhaps her generation. She was an amazing mother, I just wish she could have been happier with what she had."
If Mellor says she has tidied up the story in her own mind by putting it on stage and screen, the lessons it taught her have stayed:
"You don't know what stories are within everyone. I say to everyone, 'Talk to your mother, father, talk to them and listen to them while they're still with us.'"
And for her own mother, she has this to say: "Sometimes you can become so blinkered in a romantic notion of what love is, that you miss the very thing that you’ve got. When my stepfather died, who she'd had no real affection for, she felt bereft, and she'd talk fondly of him.
"I loved her to bits, but could have put a bit more effort into her two husbands. In fact, later, she decided she wanted to write, she headed off to creative writing class, which is where she met Jeffrey..."
It really is always the quiet ones.
A Passionate Woman is now available on DVD. Kay Mellor's The Syndicate is on BBC1 on Tuesday 27 March at 9pm.