Mum looks around the room, with its designer appliances and its double-height glass atrium. ‘That’s fine. We can handle expensive.’

For a moment, their love takes my breath away. They never gave up on me, no matter what I did. I want my son to know how that feels, too. ‘The other thing is, if it ends in some messy fight between me and Zoë, you might hear stuff about me that I’m really not proud of.’

My mother’s face doesn’t change. ‘We love you, no matter what you’ve done. You’ll understand this soon: we’re your parents and we’ll do whatever it takes.’

It takes money, and determination, and still there are no guarantees.

First, Dad hires an iffy private detective from his investigative TV days to find out where Zoë gave birth.

While we wait, we plan for the next stage. Apart from when I was first sick, it’s the only time I can remember us acting the way families do in the movies: cheerleading and urging each other on whenever one of us begins to doubt that this will work out.

It’s a fortnight before the detective confirms that my boy exists and was actually born here in Brighton. While I was imagining some fairy-tale future with Kerry, my son was coming into the world only a couple of miles away.

It feels as though I should have known, somehow.

But now I do, the world seems different.

The helpline tells me to do everything by the book: fill in the forms in my best block capitals, agree to the DNA test, wear a suit and a passive smile to all meetings, agree my past has been problematic, work to prove I deserve a role in his life.

As his mother, Zoë doesn’t have to prove that to the social workers, but she’s not making it easy for herself. Her decision to drop out of the system and not get any antenatal care has meant our child was born an addict. Edwina, my social worker, says she did well after the delivery, agreeing to rehab and even expressing milk for the baby. But now she keeps going AWOL and it’s not looking quite so promising.

Meanwhile, I wait some more: for the results of the DNA test, for my assessment, for crumbs of news about my son’s progress. He doesn’t even have a name yet, and Zoë can wait till the beginning of February to register his birth. I don’t know if it’s because she’s waiting deliberately, or because her life is still chaos.

‘We can’t just call him baby,’ my mother says, ‘but a name feels wrong, because we’ll get used to it and then it’ll be weird when she calls him something else.’

‘Spud,’ Dad says. ‘That’s what we called you before you were born. The baby could be Son of Spud.’