We used to think that thermal undies were something that only our dads wore, but the joke is truly on us, because a good pair of thermals does wonders when there's a chill outside.
As the temperature continues to drop in the UK, we've been on the hunt for a good pair of trusty thermals that won't break the bank and have found great sets for both men and women at M&S.
There's never been a better time to stock up too, as the Met Office issued a warning on 5 December that it could plummet to -6C in some parts of the UK, with snow expected in Scotland.
To ensure you stay warm and cosy, here are the base layers we think are worth adding to your basket for winter, from bargain £16 thermal leggings to rather chic looking thermal tops.
Why we rate them
The Heatgen Plus™ Fleece Thermal Leggings first caught our eye because of their bargain price tag, however, a quick scroll through the reviews and it's easy to see why women are buying multiple pairs, one happy shopper said: "Absolutely love these, can hardly take them off! Bought another pair."
Made with M&S' special Heatgen Plus™ thermal technology to help keep the heat in, the lightweight leggings are not only designed to keep out the chill, but also for comfort as they have added stretch and feature a super-soft fleece brushed on the inside to be extra cosy.
Buy it: Heatgen Plus™ Fleece Thermal Leggings | £16
The matching £16 top has the same Heatgen technology and features a stylish high neck silhouette, so you don't need to worry about the cold breeze finding any gaps.
The review section shows everyone is equally as enthusiastic about the affordable design.
"This is the best ever thermal top. I have worn this and washed it several times, it's still amazing. Keeps me toasty under my jumpers/coat when at work (stone floors and no heating!!) I love it so much I've now got 4!!" reads out favourite review.
Buy it: Heatgen Plus™ Fleece Thermal Turtle Neck Top | £16
The affordable menswear thermal set
The menswear thermal set is equally as impressive.
M&S' black thermal long johns are an absolute bargain for £18 and have nearly 200 reviews to prove they're excellent value for money.
For ultimate comfort they're made from an insulating brushed-back cotton blend to help them be breathable as well as super comfy.
"Bought for winter walking and golf. Comfortable and warm," reads one review. While others praise them for being soft and quick drying, saying they "will definitely buy again".
The popular long johns also come in four colours: black, white, grey and berry.
Buy it: Thermal Medium Warmth Long Johns | £18
M&S' matching Thermal Medium Warmth Long Sleeve Top is also only £15 and comes in the same four hues.
It's also highly rated for its warmth and comfort and and has over 200 reviews, one customer saying: "My husband has worn them every winter for years and they last very well."
Buy it: Thermal Medium Warmth Long Sleeve Vest | £18
The brand has also recently bought out a new version.
The latest £25 two-pack Heatgen™ Light Thermal Long Sleeve Top features M&S' new Our Heatgen™ technology, which helps to lock in body warmth while also having four-way stretch for ultimate movement and comfort.