The "biggest victim" of the 1967 Rolling Stones drugs bust near Chichester

Emer McDaid, whose task it is to embody Marianne on the stage, stresses that the whole thing ruined Marianne.

“Mick and Keith emerged as gods from the whole thing, but Marianne was 21 years old and the mother of a one-year-old and she said that it was the beginning of the end of her life. Shortly afterwards she became homeless and addicted to heroin. The country that had lauded her as an It girl turned on her.

“Marianne Faithfull at that point was a real kaleidoscopic oxymoronic kind of woman. She was a kaleidoscope. You read about her and you get an idea about her but she's like one person with one person and then becomes somebody else when she's with someone else. Suddenly the image turns and there is a whole other picture. And that’s the thing that comes across really strongly in the play, who she is on a human level and not just the fame hungry person that people saw. Mick and Keith came out as his heroes. But she is left being called a jezebel and a slut. It damaged the absolute heart of her femininity. She became this completely damaged woman. She was this great dichotomy, the daughter of a baroness and yet the physical embodiment of rebellion but then everyone turned against her. It's OK for men to behave in the way they did, but absolutely not for women and she became the scapegoat.

“At the start of the play she's one of the boys. She is Mick and Keith’s mate and not just a lover or a girlfriend. She is joyful and she's exuberant and she's on a high at Redlands, a little bit high but in a good way. And the high has brought out the most beautiful innocence in her. She was only 21 and the whole world was ahead of her. She was going to be the next great actress.”

But then with the drugs bust everything changed – and the folklore lives on in the most damaging way: “I can't tell you how many messages I've had about Mars bars. She has said that it was a dirty old man's fantasy. It never happened. It's completely fabricated and, as I say, it ruined her life. It just never happened but it was seen as so much part of what happened. She was naked and was wearing a fur rug but that wasn't what people went for. They went for the worst thing and that was something that hadn't even happened, the Mars bar.”

As for playing her: “I am a natural Irish redhead. I've only ever had my hair dyed once in my life and that's for this play. I'm trying to look like her and I'm trying to stick quite closely to how she was but I do have perhaps more freedom because people don't know her as well as they do Mick and Keith. I'm really excited about bringing out her humanness.”