It’s not her fault, though, none of it, and I know how hard she tries because I’ve been watching her my whole life. But it wasn’t until I was about seven and started occasionally visiting other kids’ houses that I realised not everyone’s mother took up residence under a duvet on the sofa for weeks at a time. Lou’s had numerous holidays abroad on our sofa over the years. Sometimes she even likes to research a cover story, flicking through travel brochures I’ve picked up on the way home from school, memorising restaurants and landmarks in various sunny locations, so she won’t be caught short if any of her colleagues ask questions. We tell ourselves it’s almost as good as the real thing and there’s no lining up for passport control.

Lou’s boss Jackie has covered for her for years, by letting her have more sick days than she’s officially allowed and approving her annual leave at very short notice. Once, Jackie called around to drop off some flowers and a couple of forms for Lou to sign, and when she was leaving, she gave me a huge hug and told me it wouldn’t always be this way. ‘I promise,’ she said. Jackie’s the only one who knows the truth about Lou’s sofa holidays and she’s a sweet woman for someone so deluded.

Sometimes I try to imagine myself in my mother’s place on that sofa. What I’d do if it were my skin wrapped around my bones so tight it felt like somebody could bounce marbles off it; or if it were me who felt like I was living in the mouth of a whale trying to get out through the gaps in its teeth, like krill. I think about whether I’d do things any differently, or any better than her, and I really don’t know.

Because the thing is, when I look in the mirror, I can’t always see my dad, but I can see the blueprint of Lou so clearly I sometimes wonder if we’re actually the same person, just siphoned into two bodies. The theory adds up when stuff happens like I can’t sleep because I’m worrying about Lou’s guys from the housing centre and whether they’ve all got somewhere safe to go that night. Or when I’m scared to go home after school when she’s on one of her sofa breaks in case she’s still holding on to the same cup of tea I made her eight hours ago, but then I nearly kill myself in my hurry to get back there.

And the truth is, when I see my mother looking back at me from the mirror, it scares the shit out of me on the one hand and makes me prouder than all get-out on the other. So I really, really don’t know.

When I was eleven a very kind doctor once told me I should just be there for Lou. We were sitting in his office and Lou was crying, and I was churning inside like an industrial washing machine trying to pretend everything was normal.