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Heatgen™ Medium Thermal Long Johns

Product code: T148814N

About this style

These thermal long johns provide medium warmth with a regular fit, perfect for cooler days as a base layer underwear. The insulating brushed-back fabric offers breathability for lasting comfort, while comfort seams ensure a snug feel. Featuring Heatgen™ technology that helps generate and retain body heat when temperatures drop, making this undergarment ideal clothing for layering. M&S Collection: easy-to-wear wardrobe staples that combine classic and contemporary styles.

Medium warmth for wrapping up in moderately cold conditions.

M&S

Heatgen™ Medium Thermal Long Johns

€26

Colour

Size

Also available in: Long Sleeve and Short Sleeve
Free standard delivery over €75

Reviews (601)

4.7

73% Recommended this product

Mentions
25 March 2026CAZZERB

Great quality

Originally posted on marksandspencer.com (UK)

Yes, I recommend this

Bought a pair for my rather discerning 94 yr old father - he loved them so much he bought a further 3 pairs!

Reviewer Ratings

Comfort

Excellent

Helpful?

Reviewer Ratings

Comfort

Excellent

24 February 2026Mr207

Just right but all one length

Originally posted on marksandspencer.com (UK)

Yes, I recommend this

Comfortable and warm. Only downside is the one length for all. A choice of lengths would have been better.

Reviewer Ratings

Comfort

Good

Helpful?

Reviewer Ratings

Comfort

Good

18 February 2026Rainbow26

Perfect

Originally posted on marksandspencer.com (UK)

Pleased with my purchase these are soft and warm and will be ideal under trousers for a forthcoming trip to the Artic

Helpful?

14 February 2026Marion4

Heathen Thermals

Originally posted on marksandspencer.com (UK)

Yes, I recommend this

My husband feels the cold a lot since he has got older and these thermals have meant he can still potter around in his shed. They fit him a treat and the main thing is they keep him warm

Reviewer Ratings

Comfort

Excellent

Helpful?

Reviewer Ratings

Comfort

Excellent

13 February 2026mimi123

Good quality and sizing.

Originally posted on marksandspencer.com (UK)

Yes, I recommend this

Good quality item. Sizing was good. Bought M for husband who wears 32 waist and has athletic build. They fitted well. He's pleased with them.

Reviewer Ratings

Comfort

Excellent

Helpful?

Reviewer Ratings

Comfort

Excellent

11 February 2026GeMc84

Great additional layer

Originally posted on marksandspencer.com (UK)

Yes, I recommend this

I bought this for our trip to Copenhagen this February as the weather was very cold. My husband liked it, he said it kept him warm and was very soft and comfortable.

Reviewer Ratings

Comfort

Excellent

Helpful?

Reviewer Ratings

Comfort

Excellent

05 February 2026Jonmig

Nice quality bottoms

Originally posted on marksandspencer.com (UK)

Yes, I recommend this

Excellent product , very comfortable and warm , great fit , heat retaining , nice quality

Reviewer Ratings

Comfort

Excellent

Helpful?

Reviewer Ratings

Comfort

Excellent

31 January 2026Apantoja

Good quality

Originally posted on marksandspencer.com (UK)

Gave it to my parter as a present and he says it is very comfortable and a nice material

Helpful?

31 January 2026BB1695

Warm

Originally posted on marksandspencer.com (UK)

Yes, I recommend this

Warm and very comfortable I’m 34 waist and they fit perfectly size medium recommended

Helpful?

29 January 2026Lin 39

Great value for money

Originally posted on marksandspencer.com (UK)

Yes, I recommend this

Very warm good quality would definitely recommend good price and quick delivery

Reviewer Ratings

Comfort

Excellent

Helpful?

Reviewer Ratings

Comfort

Excellent

28 January 2026Gete

Great quality

Originally posted on marksandspencer.com (UK)

Bought for my husband and he’s very happy with them

Reviewer Ratings

Comfort

Good

Helpful?

Reviewer Ratings

Comfort

Good

27 January 2026kay1943

Perfect for me

Originally posted on marksandspencer.com (UK)

Yes, I recommend this

Keeps me cosy while watching rugby in a cold stand. Legs long enough too , (inside leg for trousers 32"). Thank you, Marks.

Reviewer Ratings

Comfort

Excellent

Helpful?

Reviewer Ratings

Comfort

Excellent

25 January 2026TheBestInTheWest

Warm and convenient

Originally posted on marksandspencer.com (UK)

Yes, I recommend this

Husband likes them. Flies are convenient. Long John's kept him warm when our heating system broke down in January.

Reviewer Ratings

Comfort

Excellent

Helpful?

Reviewer Ratings

Comfort

Excellent

23 January 2026Foxy52lady

Perfect fit

Originally posted on marksandspencer.com (UK)

Yes, I recommend this

Lovely soft material true to size good quality and not overly expensive

Reviewer Ratings

Comfort

Excellent

Helpful?

Reviewer Ratings

Comfort

Excellent

21 January 2026Boab1

Cosy

Originally posted on marksandspencer.com (UK)

Yes, I recommend this

Excellent quality, great fit, warm and comfortable

Reviewer Ratings

Comfort

Excellent

Helpful?

Reviewer Ratings

Comfort

Excellent

20 January 2026Criticalchris

Comfortable and easy to wear

Originally posted on marksandspencer.com (UK)

Yes, I recommend this

These are really comfortable and unlike other makes are easy to get on and off. Excellent value

Reviewer Ratings

Comfort

Excellent

Helpful?

Reviewer Ratings

Comfort

Excellent

20 January 2026AngelinaBallerina13

These are very soft to wear and a great fit.

Originally posted on marksandspencer.com (UK)

Yes, I recommend this

These are very soft against the skin, keep the warmth in and also a great fit.

Reviewer Ratings

Comfort

Excellent

Helpful?

Reviewer Ratings

Comfort

Excellent

20 January 2026NannyJan65

Great quality

Originally posted on marksandspencer.com (UK)

Great product, ordering another pair in a different colour

Helpful?

19 January 2026Johnchp

Comfortable

Originally posted on marksandspencer.com (UK)

Yes, I recommend this

Good fit, good quality and very comfortable to wear.

Reviewer Ratings

Comfort

Excellent

Helpful?

Reviewer Ratings

Comfort

Excellent

15 January 2026Johno17

Great quality

Originally posted on marksandspencer.com (UK)

Yes, I recommend this

Great value and my elderly brother now has warm legs when out walking the dog.

Reviewer Ratings

Comfort

Excellent

Helpful?

Reviewer Ratings

Comfort

Excellent

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