I am sitting in my office, reading an information sheet titled Understanding Flexible Sigmoidoscopy. Although I’ve read it twice already, I keep skipping sections that I think won’t appeal to me. I’ve still managed to grasp its underlying message, which is: “You haven’t had a camera up your arse until you’ve had our camera up your arse.”

A week later, I find myself in a hospital examination room. A nurse explains the entire procedure in a manner that leaves me unable to skip the bits that don’t appeal to me.

“Here are your dignity shorts,” he says. “I’ll just leave you to pop those on.”

Once I’m alone, I examine the shorts carefully. It is not immediately apparent how they might confer, or even preserve, dignity. I send my wife a text that says, “Just changing into my dignity shorts.” Her reply says, simply, “pic?”

Eventually I am escorted down the corridor to another room, where the nurse tells me to lie on my left side with my knees drawn up. “Like a baby,” he says. Once I’m on the the table, another nurse adjusts the large ArseCam screen so that I have an unobstructed view.

An hour later, I am home. “How was that?” my wife asks.

“Fine,” I say. “I mean, you’re always quite conscious of the fact that, out of four people in the room, you’re the only one with a camera up his arse.”

On Sunday, my wife’s sister and my niece come to lunch, bringing fresh asparagus from the country. My sister-in-law tells us a long story about hiring some kind of spiritualist, a self-proclaimed bringer of light, to banish a ghostly presence from an attic bedroom. “The thing is,” my sister-in-law says, “she was quite overweight, and I had to lead her up all these winding stairs.”

“You imagine them being thin,” I say, “but I guess that’s a stereotype.”

“When we get to the top, she’s like, ‘There’s definitely something here – have you noticed the change in my breathing?’. And I’m like, ‘Yes, I have!’ And she’s like, ‘I think I need to sit down for a minute.’”

“How much does she cost?” I ask.

“You pay what you think it’s worth,” my sister-in-law says.

“And what did you decide it was worth?” my wife says.

“Fifty,” her sister says.

“You paid sixty,” my niece says.

“I did,” my sister-in-law says. “I paid sixty.”

Once, I would have felt an obligation to pour scorn on such a story, to mock the credulousness of the participants, to roll my eyes at the idea of confronting a ghost and, with help of two spirit guides, ushering it from the wardrobe into the light. But over the years I’ve realised that this impulse springs not from a desire to defend rationality, but from an unattractive urge to spoil other people’s fun. When conversation turns to the spirit realm, I mostly feel excluded, because I have nothing to contribute.

Something occurs to me. “Speaking of bringing bright light to bear on a mysterious netherworld,” I say, “I, too, have been on a journey.”

“Oh, Christ,” my wife says. “He’s going to talk about his colon.”

“Is he?” my sister-in-law says.

“A world where all is silent,” I say, “apart from the sharp tear of the velcro flap at the back of your dignity shorts.”

“Do you want to see him in his dignity shorts?” my wife says. “I’ve got a picture.”

“Imagine a dark corridor, full of twists and turns,” I say. “Potential malevolence lurking around every corner.”

“But everything’s fine,” my wife says.

“Not quite,” I say. “Because it turns out they have an even bigger camera.”