Had Marsha been a different type of woman, she would be consumed with bitterness about the way Jagger treated her. When they met, he was obsessed with her, and it is widely thought that he wrote one of the Rolling Stones’ most famous songs, Brown Sugar, about her. But when Karis was born, in 1970, Jagger refused even to acknowledge paternity, much less play any part in his daughter’s life. He only recognised Karis as his daughter more than a decade later, and then only after a bitter court battle by Marsha.
Today, Karis and her father are close, but the rejection was all too public. At the time, Marsha was determined that her daughter should know her father. Heartbreakingly, she even told Karis ‘that’s your daddy’ when Rolling Stones songs came on the radio.
I ask if she felt any guilt for bringing Karis into the world in what now seems like such uncertain circumstances.
Marsha shakes her head. ‘No. What happened was not my fault. Besides, whatever happened with Mick, she went on to have such a fabulous life.
There were uncles and friends of mine who adored her. I never thought she was deprived.
'In fact, now I think she is incredibly lucky. She could have had all kinds of fathers and she had Mick. Now he can really appreciates who she is and what she has become. I know that she would be a different person had he been around all the time, and, in a way, with hindsight, I can say, “Wasn't it lucky that he wasn't there.”'
I ask if she means it was lucky that Jagger wasn’t there to screw up Karis’s life.
She nods, and says, “She was 12 - formed - when they got to know each other. What are you going to do to a child of 12? You are going to have some influence, but there is already some core stuff pulled together by then.’
That’s quite a damning opinion of Jagger, then? She shakes her head.
'It's not about him. It's about his position, his lifestyle, his career, his choice of friends. I mean, my daughter had an incredibly stable upbringing. I read to her every night, sang to her. I have no idea how different things would have been if Mick had been part of her life, but I know that the influence of celebrity and all that goes with it is difficult for children.'
She tells me that she went out of her way to turn Jagger into a hero figure for her daughter - ‘as all dads should be’ - even when she felt like screaming about what a rubbish father he was.
'When you have a child, you put them first, whatever. All your own feelings have to take second place. How I raised Karis is now what I'm proudest of.
Today, she is part of the infamously convoluted Jagger clan, and seemingly happy to be so. She waves away any notion that there is anything unhealthy about the way the Jaggers live.
'No, these are siblings who share a notorious father, but they deal with each other in beautiful ways. All the kids were at Karis's wedding, you know. Jade (Jagger's daughter with his first wife, Bianca) was the maid of honour. I remember standing up and saying something important - that modern life has created new kinds of families, and the crucial thing is to do the best you can with that. And things have worked out pretty well. Mick is a grandfather, and he's a good one. Do I have regrets about getting involved with him? Are you kidding?'