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M&S

Heatgen™ Medium Thermal Long Johns

£20

Sorry, this item is no longer available

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.

Details & care

Style

Regular fit

Button fastening

Features

Thermal

Soft and cosy brushed fabric that keeps warmth in

Heatgen™ technology

lightweight and supersoft, designed to keep you warm when the weather gets chilly

Composition

50% cotton, 26% polyester and 24% viscose (exclusive of trimmings)

Care

Wash at 40°C

Do not bleach

Tumble dry medium temperature

Iron at medium temperature

Do not dry clean

Delivery, collection & returns

Christmas delivery and collection last-order dates

Standard Delivery

Order by Saturday 20th of December

Nominated Day Delivery

Order by Tuesday 23rd of December

Store Collection

Order by Tuesday 23rd of December

Delivery

Standard

UK Standard Delivery is available for £3.99 or free on orders over £60 (excluding furniture).

Nominated Day

UK Next Day Delivery and UK Nominated Day Delivery (excluding Northern Ireland) are available for £5.99 (excluding furniture)

Collection

Collect from store

Store collection is free on all fashion, home and beauty orders.

Returns

UK returns

Free

Exclusions apply

Full delivery and collection informationOur returns policy

Reviews (571)

4.7

73% Recommended this product

Mentions
09 December 2025Mje59
Verified Purchase

Great product

No, I don't recommend this

Excellent quality and really warm. Definitely recommend

Reviewer Ratings

Comfort

Excellent

Helpful?

Reviewer Ratings

Comfort

Excellent

09 December 2025SueNana
Verified Purchase

Keep snug and warm in these

Yes, I recommend this

Very warm and perfect for the less mobile on cold winter days also helps to save on the heating bills

Helpful?

09 December 2025Glyn73
Verified Purchase

Great quality at a great price. Thanks M&S

Yes, I recommend this

Excellent quality at a good price. M&S rarely disappoints.

Reviewer Ratings

Comfort

Excellent

Helpful?

Reviewer Ratings

Comfort

Excellent

05 December 2025Zilpah
Verified Purchase

Great Colour

Yes, I recommend this

Nice to find these thermal pants in a different colour, ideal as an extra layer for going to watch the football in the cold weather.

Reviewer Ratings

Comfort

Excellent

Helpful?

Reviewer Ratings

Comfort

Excellent

03 December 2025Fiab
Verified Purchase

Great replacements

Yes, I recommend this

Bought for my husband, who liked the new colours and hasn’t complained about them, so presume he is happy.

Reviewer Ratings

Comfort

Good

Helpful?

Reviewer Ratings

Comfort

Good

30 November 2025Drew65
Verified Purchase

Drews

Yes, I recommend this

Good quality item and good value for the money 👌 .

Reviewer Ratings

Comfort

Excellent

Helpful?

Reviewer Ratings

Comfort

Excellent

29 November 2025L p Loy
Verified Purchase

Great Value

Yes, I recommend this

Excellent value product. Great fit and ordering process (in store collection) was super fast .

Reviewer Ratings

Comfort

Excellent

Helpful?

Reviewer Ratings

Comfort

Excellent

21 November 2025Ray244
Verified Purchase

Don't bother

No, I don't recommend this

No real warmth felt even under additional clothes.

Reviewer Ratings

Comfort

Average

Helpful?

Reviewer Ratings

Comfort

Average

16 November 2025MikeTL
Verified Purchase

Brilliant product

Yes, I recommend this

As an arthritis sufferer the warmth from these thermals is so good and helpful

Reviewer Ratings

Comfort

Excellent

Helpful?

Reviewer Ratings

Comfort

Excellent

16 November 2025LGJG
Verified Purchase

Good quality.

Yes, I recommend this

Good quality, nice fit. Very soft fabric and comfortable round waist.

Reviewer Ratings

Comfort

Excellent

Helpful?

Reviewer Ratings

Comfort

Excellent

16 November 2025Frinqui
Verified Purchase

Nice and warm

Yes, I recommend this

Nice and warm for under trousers when working outside

Reviewer Ratings

Comfort

Excellent

Helpful?

Reviewer Ratings

Comfort

Excellent

12 November 2025CHEPI1
Verified Purchase

Warm Soft and very cosy

Yes, I recommend this

Perfect to keep warm when the weather gets colder.

Reviewer Ratings

Comfort

Excellent

Helpful?

Reviewer Ratings

Comfort

Excellent

12 November 2025ILoveClothesandShoes
Verified Purchase

Great and long-lasting quality.

Yes, I recommend this

I have been buying Heatgen clothes from M%S for a longtime. I find them so warm, cozy and comfortable. They are wonderful to use in the winter months at home or when out. It saves using the heating all day. They are so good, I now have my husband buying them! I recommend them to anyone. Can you please provide more colours?

Reviewer Ratings

Comfort

Excellent

Helpful?

Reviewer Ratings

Comfort

Excellent

12 November 2025Froggy90
Verified Purchase

Good quality

Yes, I recommend this

Good for in my wheelchair during the cold winter months.

Reviewer Ratings

Comfort

Excellent

Helpful?

Reviewer Ratings

Comfort

Excellent

07 November 2025JDCMH
Verified Purchase

My go to for thermal underwear!

Yes, I recommend this

Always purchase thermal underwear from M&S, for my husband. Great quality, fit and price. As long as he’s cosy, that’s fine by me.

Reviewer Ratings

Comfort

Excellent

Helpful?

Reviewer Ratings

Comfort

Excellent

04 November 2025MisterHarry
Verified Purchase

Prefer the previous design

Yes, I recommend this

Material is good but possibly a few microns thinner than a few years ago, like the new style elastic waist band but not the one button fly front. The previous Y front style fly is probably more expensive to produce, more material and time.

Reviewer Ratings

Comfort

Average

Helpful?

Reviewer Ratings

Comfort

Average

30 October 2025BamfordL
Verified Purchase

Good quality

Yes, I recommend this

Bought these for my husband. Said they are very comfortable, keep his legs warm and good quality. Better than cheaper brands.

Reviewer Ratings

Comfort

Excellent

Helpful?

Reviewer Ratings

Comfort

Excellent

23 October 2025
Verified Purchase

Really pleased with the quality of this garment.

Yes, I recommend this

My husband hasn't worn these yet, but really pleased with quality of this garment.

Helpful?

12 October 2025chabod
Verified Purchase

Pleasantly snug fit

Yes, I recommend this

Need to be longer … good snug fit … need coloured options in maximum warmth apart from black, grey n white

Reviewer Ratings

Comfort

Good

Helpful?

Reviewer Ratings

Comfort

Good

11 October 2025GCOLeary
Verified Purchase

These will definitely keep me warm

Yes, I recommend this

I wasn’t sure about the colour but it’s fine for me

Reviewer Ratings

Comfort

Excellent

Helpful?

Reviewer Ratings

Comfort

Excellent

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