I’m on my way into the supermarket when a young woman pokes her head out of a screened cubicle and asks me if I would like to come in for a health check. How long will it take? Fifteen minutes, says she, so I think: why not? I am healthy as anything for my age. I have never had high blood pressure or cholesterol, barely smoke or drink, am not overweight, the dog forces me to take regular walkies. This test will just confirm what I know already, quell any anxieties and make me feel confident and happy about the length of my future. So I go swanking in, expecting only good news.

I don’t get it. The news is all bad. Everything is up: blood pressure, cholesterol, weight, risk of dropping off my perch. I find that the odd cigarette works as a fairly effective laxative, which is the reason I smoke. “Can you give them up?” asks this doctor. Yes. And do I eat many cakes? Yes, I love cakes. Cut those down, and no more croissants, says she strictly. No more full-fat milk. And go to the doctor. I will, I will, I swear it. I buy some spartan shopping and go home to a dismal, restrictive and rather terrifying future.

And guess what? That night, I have an odd, new stabbing pain, just where my heart is, and I can feel it thumping scarily at bedtime, I have breathing difficulties and my left arm has gone a bit numb. Help! And who is that ghostly figure shrouded in black at my door?

Isn’t it difficult to control one’s mind? Apparently, a “delusional belief” is hard to dispel. In a 60s study, The Three Christs of Ypsilanti, psychologist Milton Rokeach got three people, all convinced that they were Jesus, to live together for three months. After which they all still thought they were Jesus. So I went to the doctor, who laughed rather a lot, and dispelled my belief. I had no terminal conditions.

Always make sure you are of sound mind before checking on what you think is a sound body.