Your daughter falls in love with your best friend's husband. Whose side are you on?

As I walk through the front door of my daughter Scarlett's house, looking forward to the birthday lunch we have planned, nothing can prepare me what I see. Andrew is here too, my best friend's husband ... Scarlett and Andrew say they are in love. Despite the 25-year age gap, they want to be together.

My best friend Philippa and I have known each other for 50 years. Our daughters are more like sisters. We know everything about each other. And Philippa's the only person in the world who knows my darkest secret.

She'd decided to leave Andrew. They'd drifted apart. My husband and I were devastated – her desire for a different kind of life broke up our happy little group – but I supported her.

Now, seeing Andrew and Scarlett together ... I can't take it in.

My husband is horrified, and my loyalties are all over the place. Scarlett begs me to keep her secret from Philippa. Begs me to understand that, despite the age gap and the way in which they came together, she and Andrew are perfect for each other.

I cannot lose my daughter over this but how can I betray my best friend? How can I risk her sharing the secret that could break apart my own family?

And what would happen if my family found out who I really am?