It was set out the old-fashioned way I’d learned at school decades ago, with Ingrid’s address at the top on the right-hand side.

Dear Paula.

Dear! I was surprised that she had brought herself to write that. Maybe she’d crossed her fingers.

Mark has asked me to get in touch to let you know some news that I’m afraid may come as a shock to you. We felt that you ought to know and not to find out by chance.

Around the time of my sister’s funeral, during the very difficult time when you and Mark were living separately, Mark had a brief relationship with a young woman called Jenny.

Jenny? Who the hell was Jenny?

A brief relationship? Did she mean a one-night stand?

Had it been revenge – payback for my poor little long-ago crush, that I’d never so much as followed through on?

I’d felt so guilty. I’d tried so hard to make it up to him. And yet he’d had a fling with someone else and had never even come close to confessing. He had slept so peacefully next to me night after night all those years… He’d shared meals with me, lived under the same roof, without ever letting it slip.

How could I not have suspected? How could he have kept it from me so completely?

He is the father of her daughter, Ava, who is now sixteen.

Ava.

Sixteen.

This girl – Mark’s daughter – had been there all along. For most of our marriage.

And where had he been? With me. At dinner parties. On holiday. Putting on his suit and going off to work. Living a comfortable, affluent, childfree existence – right up until I had Daisy, at which point it had all begun to fall apart.

Too much noise. Too much mess. Too much chaos.

And then it had become apparent that Daisy wasn’t developing in the same way as other children her age, and he had bolted. We had been in trouble, and he’d gone off and left us for dead.

‘Bastard,’ I said out loud.

When Jenny discovered she was pregnant, she decided not to tell Mark, as she knew he had gone back to you.

Jenny the martyr, the mother of Mark’s other daughter, selflessly backing off so he could save his marriage to me. How very thoughtful. How marvellously, idiotically kind. Of course, we were doomed in the long run anyway, but she wasn’t to know that, was she?

She received an offer of marriage from a longstanding admirer while she was expecting, and accepted it.

But seriously – this Jenny was something else. What kind of woman would do that? Marry someone while she was pregnant with somebody else’s kid? And what kind of man would make the offer?

Maybe Jenny wasn’t a martyr. Maybe she was Machiavelli.

Either way, she must have had something going for her. I couldn’t imagine having attracted any offers of marriage when I was pregnant. Even Mark had pretty much stopped fancying me. He’d ended up looking at me as if I was a potentially unreliable co-worker rather than an object of lust – except for the times when I was really hormonal and bad-tempered, when he’d regarded me with alarm.