This is the only item you need to master your layering game for autumn's easiest fashion upgrade

I re-discovered it this morning as I was getting dressed. Scrunched at the back of my jumper shelf, there it was – a creamy white fine gauge polo-neck jumper by Cos, and, it turns out, also the answer to my dressing needs as we properly move into autumn from today.

Why? Well, this autumn is, as we say in fashion, “a separates season,” which basically means dresses are less popular than trousers, midi-skirts, blouses, shirts and jackets.

When you’ve got to think a little bit more about how you put an outfit together, and it’s not quite cool enough to pull out your winter coat, you need some versatile layering pieces that do the job of pulling it together and keeping you warm.

Which is where the undervalued brilliance of a fine guage polo-neck comes in.

As soon as I saw my forgotten polo neck, I was instantly able to reimagine every single one of my favourite summer outfits into a stylish autumnal one, and you can too.

My pink cotton shirt and jeans combo can ride again with the addition of my white polo neck layered under the shirt. I’m wearing it now, in fact!

Ditto my navy silk blouse and beloved Uniqlo chinos. With the addition of the Cos polo-neck, my new charity-shop-find wool blazer and my recently resoled Gucci loafers, I have an outfit worthy of designer Michael Rider’s debut at Celine. Really.

I’m not the only devotee of this particular fine-guage polo-neck from Cos– it is the mainstay of Claudia Winkleman’s Traitors wardrobe, a fact revealed to us at Good Housekeeping in August of this year by her stylist Sinead McKeefrey.

This week Cos relaunched the polo neck, £45, in six colours - I love the blue patterned version - but the pale pink, olive, brown and navy are also as gorgeous as they are useful, and all are currently showing as fully stocked.

But they are not the only place to consider for this useful style staple. I love Free People’s striped cotton version, ideal if you’d like a fabric that doesn’t feel too warm, while M&S do cotton rich versions for £16.

A polo neck might not be a style statement on its own, (a fact Victoria Beckham would dispute) but layer a fine gauge polo-neck under your favourite shirts, blouses and jackets, pop on your favourite jeans, and, well, just like that, you’ll feel the thrill of being both stylish and warm this autumn, and all for less than £50.

The best fine gauge polo necks now