When the weather is this cold it can be difficult to know what to wear. Many of us are reaching for extra layers just to stay warm, and while thermals are a winter essential, not everyone wants to be stuck in bulky layers that make you look like you’re about to hit the slopes. This is why the Marks and Spencer’s Heatgen medium thermal crew neck tops have caught my eye.

Priced at £17, they’re long-sleeved and designed to keep you warm without looking like underwear. I would happily wear one of these on its own, or keep on under a jumper or cardigan when it’s particularly bitter outside, like this week.

The tops are part of M&S’ popular Heatgen range, made from fabric designed to trap warmth while still feeling soft and breathable. The styles come in different thicknesses, and as the name suggests, these are a mid-level option (the thicker version is the Maximum line).

The crew neck mediums are available in sizes 6 to 22, and come in six colours, including a newer pastel blue shade alongside more classic options like black, cream and khaki, which are easy to mix and match with jeans, trousers or skirts. Plus, the simple crew neckline also makes the tops easy to layer without it peeking out awkwardly.

Shoppers say these are a reliable winter staple. One long-time fan wrote: “I have purchased ten of these thermal vests over the last few years for myself, my relatives and friends… They are very warm and cosy for the winter.” They added that the tops have been worn by people aged “from 14 to 80”.

Another person wrote: “Very happy with the fabric, size and style of this cosy thermal wear. Can be worn either as layering or on its own.” And someone else penned: “I have just about all the colours, extremely useful for layering and wearing alone. My shirts and linen tops get a new lease of life with one if these underneath.”

A fourth shopper said: “I’ve bought four of these in different colours – they are lovely and warm but not too bulky, so can be worn under other jumpers or gilets. They have washed well and need no ironing.”

Fit-wise, some shoppers did find these a little snug and preferred to size-up for a slightly looser feel.