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M&S

Heatgen™ Medium Thermal Long Johns

£20

Colour

Size

Free standard delivery over £60

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

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 (601)

4.7

73% Recommended this product

Mentions
14 February 2026Marion4
Verified Purchase

Heathen Thermals

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
Verified Purchase

Good quality and sizing.

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
Verified Purchase

Great additional layer

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
Verified Purchase

Nice quality bottoms

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
Verified Purchase

Good quality

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

Helpful?

31 January 2026BB1695
Verified Purchase

Warm

Yes, I recommend this

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

Helpful?

29 January 2026Lin 39
Verified Purchase

Great value for money

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
Verified Purchase

Great quality

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

Reviewer Ratings

Comfort

Good

Helpful?

Reviewer Ratings

Comfort

Good

27 January 2026kay1943
Verified Purchase

Perfect for me

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
Verified Purchase

Warm and convenient

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
Verified Purchase

Perfect fit

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
Verified Purchase

Cosy

Yes, I recommend this

Excellent quality, great fit, warm and comfortable

Reviewer Ratings

Comfort

Excellent

Helpful?

Reviewer Ratings

Comfort

Excellent

20 January 2026Criticalchris
Verified Purchase

Comfortable and easy to wear

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
Verified Purchase

These are very soft to wear and a great fit.

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
Verified Purchase

Great quality

Great product, ordering another pair in a different colour

Helpful?

19 January 2026Johnchp
Verified Purchase

Comfortable

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
Verified Purchase

Great quality

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

13 January 2026Natasha 25
Verified Purchase

Good layering item.

Yes, I recommend this

Sent back to replace with the maximum weight version. These are fine but husband needs warmer ones. His others like this wash well and the fit is fine.

Reviewer Ratings

Comfort

Excellent

Helpful?

Reviewer Ratings

Comfort

Excellent

12 January 2026GARNO
Verified Purchase

Warm

Yes, I recommend this

Suitable for wear under trousers to keep warm jn this cold weather

Reviewer Ratings

Comfort

Excellent

Helpful?

Reviewer Ratings

Comfort

Excellent

11 January 2026Hurlo
Verified Purchase

Warm and comfortable

Yes, I recommend this

prompt delivery, soft and comfortable. Good to wear under golf trousers

Reviewer Ratings

Comfort

Good

Helpful?

Reviewer Ratings

Comfort

Good

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