We’re stuck at traffic lights. I change the angle of the rear-view mirror so that I can look at my grandsons. So neat-featured. So dainty. So vulnerable, with angelic blond hair and stick-like arms and legs. Clones of you. You have infiltrated and overwhelmed my family’s genes. But never mind. Whatever they look like, I still love them. With a bit of luck as they get older their faces will become stronger. More Jackson. Less Filby. For even though you have taken my son’s name and now call yourself Saffron Jackson, you will always be Saffron Filby to me.

We pull into the side road by Harry’s school. I switch off the car engine and sigh with relief as Hagrid is silenced.

‘Please can we listen to it for five more minutes,’ Ben begs.

‘No, Ben. We need to drop Harry off now, otherwise you’ll be late and your form teacher Ms Frankfurt will tell you off.’

‘Mummy would let us,’ Ben says.

‘Mummy isn’t here,’ I reply.

‘Franki would let us,’ Harry tries.

Franki. Their last nanny.

‘Franki isn’t here,’ I reply.

‘Daisy would let us,’ Ben pushes.

Daisy. The nanny before last.

‘Daisy isn’t here,’ I say, voice sharp.

Then I soften. ‘Come on, I’ll buy you some chocolate buttons to eat on the way home, if you get out of the car right now.’

So young, bribery still works. And you are strict about chocolate, Saffron, so it’s a real treat. You frequently remind me not to buy it for them, rabbiting on about diabetes. Rabbiting on about their teeth. But I take no notice. What harm can a little chocolate do? Life needs to be fun.

So, chocolate promised, I open the car door, and they edge out of the car onto the pavement. Eager little hands hold mine as we walk towards St Peter’s Juniors. As soon as we reach the playground Harry dashes off to join his friends. Ben and I return to the car to carry on our journey. This time, thankfully, without Harry Potter. That is our agreement. After dropping off his younger brother, Ben sits in the front passenger seat and Harry Potter is over for the day.

Sitting in the front is another secret treat. You only ever let the children sit in the back, for safety reasons. Despite not spending much time with your children, you are a stickler about certain things. I start the ignition and we set off.

‘When can I tell Mummy you give us lots of chocolate?’ Ben asks.

‘Never. You promised, remember. Otherwise I won’t be able to give you chocolate again. It has to be our secret.’

He wriggles in his seat. ‘I don’t like lying to Mummy.’ His voice sounds plaintive.

‘It isn’t lying. It’s just not telling her something,’ I snap.

He shakes his head. ‘Granny, it feels like lying.’