Politics, we’re told, is increasingly less defined by left and right. Rather, the terms we should be reaching for are “open” and “closed”. As it turns out, the way we wear our outerwear is just as divisive as the way we vote. In previous winters, our esteemed columnist Mr Derek Guy (AKA @dieworkwear) has posited that many coats – although not all, and not at all times – actually look better when worn undone. Which in turn feels contrary to many of us, given that the fastenings are clearly there for a reason. Not to mention that, beyond the cosy climate-controlled confines of the MR PORTER’s office, it is currently what we would classify as “brass monkeys” outside. (“Obviously, if it’s frigid out, you should fasten whatever you’re wearing,” Guy concedes.) But we’re willing to listen, if not stand still for long.

As with almost all opinions aired in these heighten times, Guy’s views have resulted in much chatter online – and not all of it the chatter of teeth. And in such polar conditions, the MR PORTER Team is no less polarised. In this bitterly fought war, in the bitter cold, we’ve become entrenched in our trench coats and doubled down in our down jackets. So, we posed this hot issue to two of our most out-spoken editors. If only in the hope that their burning passion might at least keep them warm, however briefly.

I’m sorry to break the news, but your parents lied to you: you do not need to do up your coat. I’m with Mr Guy on wearing mine undone. Although I’d go further and argue that, regardless of style, shape and proportions, all outwear looks better when left open. And while the crux of my cosy, cosseted colleague’s case will no doubt focus on practicality and warmth – perhaps the only logical argument he could make – styling and aesthetics are where my first rebuttal lies.

In my 29 years of experiencing cold UK winters, I have never once caught a glimpse of myself in a done-up coat and thought my outfit looked better for it. A closed coat almost always creates an unflattering silhouette. The only occasions when I’ve been happy to have the zip up to my chin is when I’m not too proud of what I’m wearing underneath. Like an ill-thought-out fancy dress outfit or the many times I forgot it was non-school uniform day.

Wearing a zipped-up puffer, I could be mistaken for the Michelin Man. In a buttoned-up overcoat, I’m a budget Batman. And with the toggles fastened on a duffle, I bear an uncanny resemblance to Paddington – especially if caught at lunchtime, sandwich in hand. All my coat-wearing qualms, however, are solved by simply keeping it ajar. A pop of colour from a mohair sweater or a change in texture from a pair of corduroy trousers helps to break up my outfit and solve my unwanted cosplaying conundrum.

Ah, but what of the elephant, or perhaps a more weather-appropriate mammoth, in the room – what happens when it’s really cold? The mere mention of not doing up your coat makes people jump to extremes, as if I’m suggesting abandoning the idea of using one altogether.

With my outerwear unfastened, I’m still 80 per cent covered. And the 20 per cent of me that’s at the mercy of the brisk winter air is armoured in a thick wool jumper and topped with a substantial scarf. And I can always add other insulating layers to my outfit, such as a quilted gilet, thermal waffle T-shirt or shearling-lined boots. Plus, a beanie/glove combo is non-negotiable for winter. I rest my case – but don’t close my coat.

With respect to my learned colleague, he of the wide-open midriff and flapping tails: zip it. Button up, sunshine. Fasten your trench belt and do whatever it is you do to toggles. The purpose of a coat is to keep you warm, dry and sheltered from the elements, and it can’t do that if it’s hanging open as if you want to sell me something suspicious. Done up is done properly.

Of course, coats come in a whole world of varieties, and I’m not suggesting that whatever the conditions, whatever the coat, it must be fastened right to the collar at all times. Although my daughter does take great joy in insisting I do exactly that, grabbing the zip of my bomber jacket and forcing my chin up lest she snag a hair of stubble.

She’s got the right basic idea, though – the apple doesn’t fall far from the tree for coat-doer-uppers like us – she just needs a guiding hand here and there. The logic is indeed so simple a four-year-old can follow it. And did we all not have it drummed into us from a similarly early age? The coat is your shield against the cold and the rain, and you won’t get its protective benefit if you do half a job.

We don’t all have to walk around like football managers, zipped head-to-toe, but if the weather merits a coat at all, it merits fastening. Otherwise, you could probably get away with something lighter – an overshirt, maybe, or a blazer. Neither is quite such an open-or-shut case, in my eyes: you can do, or undo them, as you please. But if it’s proper coat weather, why would you not? You’ll warmed not only by the literal fabric, but the smug knowledge that you made the right call. Look at them, you’ll think, trying to make do with a hoodie. In this wind!

What about looking stylish, you might ask? I’ll admit, there’s strong main-character energy about an open coat – Sherlock’s Belstaff, for example, wouldn’t have looked half so dashing if he’d been buttoned up. But we live in the real world, and when your puffer is billowing out behind you, you don’t look like a don, you look like you’re about to take flight.

There are wrong ways to do up a coat, sure: if you’ve got a single-breasted mac, don’t do all the buttons up and shove your hands awkwardly in the pockets, or you’ll look like a sad photocopier salesman. Zip a bomber jacket just the right amount and it’s conducive to good layering; a fastened overcoat also makes it easier to tuck your scarf in on winter mornings.

You can do your coat up a little, if you must flirt with danger. You can do it up in the middle or just at the top, if you really want. You won’t be feeling the full benefit, of course, but it’s better than nothing.