I must have been about 28 when my mother told me. She was at the sink washing up at the time and I was drying the pots. It's hard to remember what's fact and what's fiction now, but I'll try.
"We had a bit of a thing," was how she described her affair with the Polish neighbour that lived in the two-roomed flat below her. I thought I was hearing things. One minute we were talking about me and my husband having a bit of a fall out and somehow the conversation turned to Mum telling me how she'd committed adultery with a Polish fairground worker.
Now you'd have to have known my mum to realise how shocking that was. She was the most ordinary woman, very mumsy, not a vain bone in her body. She wasn't one to show her emotions, she was strong but affectionate with me and my brothers. She wasn't a man's woman, she had three sisters and was, in her own way, a bit of a feminist - way ahead of her time.
My dad had a violent streak and she divorced him when I was three, refused to wear a wedding ring, wouldn't accept money off him and refused to take 'handouts' from the state, preferring to work full time as a tailoress instead. It sounds nothing now, but you've got to remember this was the 1950s, people didn't get divorced. You married and that was it - for better or worse. I remember the other kids off the council estate making fun of me and my brother, saying we didn't have a dad.
Anyway I digress.
"His name was Craze and I loved him with every breath in my body," she continued. She'd mentioned a man and the word love in the same breath - it was unheard of for her to say that; even her second marriage had not been successful.
But even more shocking than that, I realised that tears were falling from her eyes into the washing up bowl. I tried to reassure her.
"I'm happy for you Mum, I'm glad you found someone to love."
"He was murdered."
"What? In Leeds?"
"In a fairground brawl. I've never been able to tell anyone."
It was hard to take it all in and then I realised that not only had Mum never told anyone about this affair, she'd never been able to grieve properly for the man she'd loved and lost.
For the best part of thirty years she'd held onto this grief - it had been locked in. No wonder her marriages hadn't worked and she found it difficult to show emotion. She had no trouble showing emotion now - 30 years of tears cascaded into the washing up bowl as she continued with her story. At the end of it she was exhausted.
"You won't ever tell anyone will you?" She made me promise. And I didn't - for 10 years. Then it was my younger brother Philip's wedding and I could see this really pained her as she faced a life alone with my stepfather Alan.
He was a good man and the marriage should've worked. He was the same religion (my dad was a Catholic, Alan was Jewish) and he was political - a strong socialist, but they clashed.
The look in my mother's face reminded me of the day she told me about Craze. Somehow these two events - my mother's affair and her youngest son getting married - were linked.
A play was burning inside of me and I started to write it for the West Yorkshire Playhouse. I called it A Passionate Woman - because I realised that's what my mother was.
I set it on the day of her son's wedding. Betty climbs into the loft to escape from all the arrangements and chaos and drops the flap shut! Her dead lover Craze comes to her and she relives her time again with him. Her son and husband realise she's in the loft and try and coax her down to the wedding, but she's not going anywhere - except up!
The play went into rehearsal with the glorious Anne Reid playing the middle-aged Betty. Two days before press night, I thought I should take Mum to see the play. It was essentially Mum's story, but I'd changed loads of things and I was interested to see if she realised it was her story. She absolutely loved it, wanted to see it again.
The second time she saw it, she turned to me at the end and with tears and bewilderment in her eyes she said: "This is my story."
I reassured her. "Yes, but I'm not going to tell anyone and you're not, so who's going to know?"
Then came the opening night of the show. All the press were there. The play went well and as is customary with a new play, the cast, myself and the director David Liddiment all sat on the stage to answer questions. One particular journalist kept asking me where I got the idea for the play - "Did something or someone inspire it?"
I could see my mother sat in the middle of the audience - I had to protect her and keep my promise. I replied: "Yes, someone did inspire me to write it, but I'm not at liberty to say who it was."
And then from the middle of the auditorium came -
"It was me!"
I looked up. My mother was waving her hand in the air; her eyes were gleaming with pride. "It's MY story!"
And as the press turned to interview her, I watched the years of shame and secrecy drop away. My mother came out publicly - she'd had an affair, she'd known love, she had a sexual awakening, she was A Passionate Woman.
Two years later the play opened in the West End to rave reviews. The play ran for a year at the Comedy Theatre and has toured extensively all over the world. Film rights were fought for, but I held on to them tightly as I didn't want Cher playing my mum on a rooftop in Detroit.
It's still running in Poland I think.