"Because what I can't work out," I say, "is whether to be brave and tell her."
"No," says my son, looking down.
"I feel I should tell her," I say, "obviously. But I can't really be sure how she'll react."
"No," says my son.
"If it comes out wrong," I say, "it'll sound as though I'm accusing her of being a bad mother."
"Mmm," says my son.
"And you can't do that," I say. "You can't ever criticise the way someone's bringing up their child. It causes huge rows. It breaks up friendships."
"No," says my son.
There's a pause. My son looks up. "What?" he says.
"Have you heard anything I've just said?"
"It's a new phone," he says. "I'm just getting used to it."
Well, I think to myself wearily, I should know by now that I can't compete with a new phone. Phones do everything these days – send emails, text, tweet, take photos, tell you what the weather's like. They can even phone people.
"So what have you discovered?" I say.
"Mmm?"
"What's so brilliant about your new phone that you can't listen to a word your mother's saying?"
He looks up. He blinks. He's a million miles away. I'd have more chance of getting a response, I think, as I stomp off in a huff, if I found my old Nokia and texted him.