Please tell me you have this jacket, or one very similar, already. And if not, then if you wouldn’t mind explaining what exactly you have been doing with yourself for the past four months? Because that is how long it is since the checked grey-or-beige blazer established itself as the new key piece in the wardrobe of the grown-up fashion connoisseur. At New York fashion week last September, I wore mine for the first time. By the London shows a week later, it had become front-row uniform, making us look like a lineup of fashion-swot prefects. (Which, in a way, is what we are.) At Gucci in Milan, I counted 11 versions on the catwalk. By the end of Paris fashion week, I had to have it relined, because it was falling apart. (Oh, the joys of a high-street bargain.)

In other words, if you don’t have this jacket (tailored, checked, on the grey-to-beige scale of soft neutrals) then get one. Do that, and you have my blessing to ignore all other style diktats for the foreseeable future, because the jacket will stand your look up completely by itself.

You will need clothes to wear with the jacket, but you have those already. The easiest way to wear it is as the flourish on an otherwise straightforward outfit. A pair of jeans and a white T-shirt; all-black polo neck, skirt and tights; a white shirt and navy tailored trousers. The simpler, even starker, the more chic the effect. Keep details minimal: a pair of simple gold hoop earrings, say, and a classic loafer.

I’m not wearing that look here, because I am pretty sure you can picture it without my help. I am demonstrating the other way to make a check blazer work with the clothes you have, which is by wearing it over a long-sleeved dress. I am bonkers about long-sleeved dresses, a high-drama, low-effort look that works, climate-wise, for about 10 out of 12 British months, give or take a pair of tights. But the bodycon ones feel a bit dated now, and strangely mumsy, whereas the loose ones are cool and modern but can end up a little more tarot-card reader than I am usually aiming for in the office. A blazer on top solves both issues, bringing a whole bunch of dresses you thought were on the way out back into play.

Don’t worry about “clashing” checks with graphic or floral prints: a soft check counts as a neutral. There are no excuses. I think you’ll find this jacket is required.

• Jess wears blazer, £59.99, and dress, £39.99, both hm.com. Boots, £239, kurtgeiger.com. Styling: Melanie Wilkinson. Hair and makeup: Sam Cooper at Carol Hayes Management