Not many pictures out there of this phenomenon. But Frank looks good

Ooo, there’s another one! A perfectly respectable businessman with only the bottom button of his three-button jacket done up. Just the one. Leaving the rest of the jacket flapping open.

It looks so bizarre. It creates an artificial, rippling belly of negative space, and as result is surely the least flattering way to possibly do up the buttons of a suit. Why on earth do they do it?

At first, I thought it was an aberration. One man walking towards me, his pinstripe ruined by a frankly odd buttoning. I briefly wondered why he had decided to do up just that button, and not the natural waist button, the middle button. Briefly I considered it, and then dismissed it – a mistake, an accident, certainly an exception.

Then a few days later it happened again. Someone else striding purposefully along Fleet Street, briefcase in hand, importantly talking into his mobile phone. With only the bottom button done up. This time the buttoning was so low that his tie had flapped over the fastening, like a bright dead fish.

Why? Don’t you see it when you look in the mirror? Doesn’t it strike you as odd, like doing up the top button of your shirt, and no others? Doesn’t the oddity of the effect suggest that the suit was not designed to do that?

As more examples popped up, I began to give the phenomenon serious thought. Why did you never see men with just the top button fastened? There were always a few with the top and the middle, or the middle and the bottom, but the waist button was always firmly secured.

Did the bottom-fasteners somehow feel that this arrangement gave them a deeper V, a plunging, masculine chest? They could be forgiven for thinking that (though still wrong) if the suit had a natural, soft roll. But modern, worsted business suits are true three buttons – the fastening is stiff and, unlike the flannels of old, there is little natural roll. So the artificial belly is the result.

Finally, a combination of curiosity and anger got the better of me and I asked someone. Embarassing, I know. But it was beginning to dominate every waking thought.

The gentleman in question was puzzled, then a little miffed, perhaps a tad embarrassed. He said he did it because it felt like a natural fit for the jacket, it felt snug. And there’s the rub: the jacket was too big for him, so it didn’t feel like it fitted with the waist button done up. The bottom button on its own felt better.

I’ve since found that some men go for the same odd buttoning if the jacket is too small for their belly – the cut of a jacket can mean that the bottom button fits when the middle doesn’t. It all depends on cut and on physique.

Of course, they’re all wrong. It looks silly and it ignores how the jacket was designed to be worn. Any man who wears his jacket buttoned in this way should be told to have it altered.

Fortunately, I have so far resisted the urge to tell any of them this.