My ex is having an affair with another soccer mum and I feel complicit. Do I tell the husband or keep it quiet?

‘What you do know is that you have leverage. And you can use that to make sure they know that this isn’t a limbo you’ll remain in forever,’ writes Eleanor Gordon-Smith. Painting: Jealousy by Tihamér Margitay (1892). Illustration: DEA/A. DAGLI ORTI/De Agostini/Getty Images

I left my ex-husband two and a half years ago. He told me the day we broke up that he had feelings for a married woman and she for him. I knew. It was part of the reason I wanted to leave him, along with a very long list of ways in which our marriage was no longer serving either of us.

A few months later he started actively (but covertly) pursuing this woman, who is a mum in my son’s sports team. Apart from my ex and this woman, I am pretty sure I am the only person who knows.