It was mentioned by Bellos in BBC documentary Angry Wimmin
I haven't seen the documentary, but she explains more about what was going on then in this interview. As thirdfiddle said, she didn't want to leave them, but she felt she had no choice.
www.theguardian.com/world/2006/feb/15/gender.andrewanthony
The viewer is left wondering why another option was not explored. Why didn't she abandon separatist feminism and take both children instead? "I'm a student," she tells me, slipping into the live action of the present tense. "I've got no money. My husband has the house, he loves the children. In those circumstances do you remove your children from their home, from their father, to take them where? To live on the street? I wanted him to leave the house, and then he could have seen the children."
She says it's still a painful topic more than 25 years later. "I remember we had agreed I would come and see the children every day and put them to bed. After about a week, he stopped it. So the terms on which I went were changed."
There was a divorce and she fought for custody but gave up when the tussle became too bitter. "I could not bear it. I would not have my children used as pawns to the hurt between us so I withdrew my claim and got some limited access. I got ulcers for the first time. But over the years my relationship with my children strengthened." Now, she says, she's on great terms with both her son and daughter, and she sees her daughter's three children all the time.