Some years ago I made myself a simple rule based on experience: never buy footwear online. I have proved the worth of this rule several times since, by breaking it. But I never learn the lesson. Last year I paid a substantial sum for a pair of smart black shoes which raise a blister the size of a 10p coin on my right heel whenever I walk more than a hundred metres in them. Luckily I only wear these shoes to funerals, which are largely seated affairs. One day I may build up a tolerance to them, but I don’t know how many more people will have to die before that happens.

My wife and I are going on a holiday with an itinerary that calls for walking shoes. It is a matter of some debate whether we actually own walking shoes.

“All shoes are walking shoes,” I say. “Except maybe my black ones.”

“These are like stiff trainers with special soles,” my wife says. “I’ll send you a thing.”

She emails me a link to the product page of a unisex hiking shoe that looks like some kind of amphibious landing craft. They have them in my size, although a little AI advice box under the picture suggests that given all the available evidence, my ideal fit would be half a size smaller. Ignoring both this recommendation and the voice in my head repeating my own rule, I click Add to Basket.

By the next afternoon two new pairs of shoes have arrived – mine and my wife’s, which are exactly the same but hers are smaller. Slipping on the right one I feel immediately vindicated: half a size smaller would have been preposterous; the shoe is a perfect fit.

Except: there’s a little vertical seam inside, up at the pointy end, that brushes the tip of my big toe with every step.

“It’s not bad, but it’s noticeable,” I say.

“Mine don’t have seams,” my wife says. “They’re fine.”

I put on both shoes and walk around the house.

“It’s a little weird, but nothing major,” I say. “Maybe they just need breaking in.”

I wear the shoes up and down the stairs, and to and from the shops, and for the rest of the evening. They seem fine. But the next morning my toe tips are so bruised that I can’t bear to put them back on.

“You’ll have to send them back,” my wife says.

“But I’ve been to the shops in them,” I say.

Time is tight, and I cannot think of a possible way to justify the immediate purchase of another pair of shoes. Late that night, unable to sleep, it comes to me: this is how you will finally learn the lesson – not from blisters or bruises, but from the very real pain of paying for shoes twice.

The next morning I find myself in a sports shop, staring at the display. The bewildering number of options is easily whittled down when I apply my budget as a filter – it leaves three shoes, one of which is the model I have at home. A sales assistant appears to find me wearing two of the shoes on my hands like mittens.

“I’m just checking the insides,” I say. “Because sometimes there’s a seam.” He doesn’t say anything. I hold up my shod left hand.

“Do you have these in a 9?” I say.

On my way home carrying an oversized branded bag, I wait for the shame of owning two identical pairs of shoes – one with seams, one without – to descend on me. But I don’t feel any shame; I feel like a swell.

A woman in a long coat approaches from the other direction. I step to one side to let her pass, but she stops in front of me.

“So now we’re building mansions, are we?” she shouts, indicating the two large houses we happen to be standing in front of. Her coat is zipped up to her chin, and she’s wearing a hat and sunglasses. All I can see of her is her eyebrows. She is waiting for an answer.

“I know, right?” I say.

“It’s ridiculous!” she says. “I’ve lived here for 30 years!”

I look up at the houses in question: both were clearly built in the late 19th century.

“I guess the houses were here already, so … ”

“You have to wonder,” she says, eyebrows rising sharply, “where these people are getting their money.”

“You do,” I say.

“I think we might be surprised!” she says.

We carry on in opposite directions, both smiling. At the corner I look back up the road to make sure she doesn’t see which way I’m turning.