When I was a child and my parents separated, I went on walking holidays with my dad. My rubric’s always been to walk from home – I’m not a rambler. It’s about a sense of being and place and engagement with the environment around me.

I like wild swimming, particularly in the sea – I swim out, then float and look at the horizon. I think that’s extremely good for the imagination. I still cycle even though I was knocked off my bike a few years ago, but mostly in the summer – it’s too dangerous in the winter in London.

I’m on meds for a blood condition, which lowers my immunity so I can get a bit snippy with people if they’re breathing snot in my face. I’ll say: ‘Look, it’s really not great for me to get a cold.’

At 56, I’m up a few times in the night because of prostatitis. I have terrible trouble sleeping and I’m guilty of all the things we tell our children not to do – I stay online, I have my phone next to the bed as I’m concerned about my kids and want them to reach me.

You’ve got to make your peace with getting older. It’s the key to good mental health in later years. In adjusting to it lies a great deal of acceptance of mortality and the reality of your life.

I’m not 100% vegetarian, I’m that awful thing they call a flexitarian. I will have a bit of fish or meat because there’s nothing else available. Red meat just started to look unappealing. The ethical stuff is secondary to an aesthetic reaction to it. It’s eating a corpse and having it rotting inside you.

I’m an unlikely health guru what with 20 years of serious polysubstance abuse, but all things being equal I’ve had a healthy life of being Dorian Gray – my fittest years were my 40s, everything went into reverse. All you have to do is walk a bit more and eat a bit less and you’ll be fine. And don’t smoke.

Phone by Will Self (Penguin, £8.99) is published on 1 March