One in three British women go to the high street giant to buy a bra and they are the market leader of lingerie in the UK.
Bras are hugely popular and important to M&S and they fit 900,000 customers per year (that's 2 customers every minute) to make sure they’re wearing the best size, shape and design for their bust.
And there's one bra for fuller busted women that's got their customers' seal of approval.
But this bra isn’t from Rosie Huntington-Whiteley's gorgeous range, nor is it from their hugely popular Boutique collection.
For £22 and in sizes 32 - 44 and cup F - H, the bra comes in black, white, rose quartz and grey blue and has 1,188 5 star reviews.
One very satisfied customer said they had “converted to this style for good. So comfortable.”
She also added: “Have worn the Flexi fit underwired bra for quite a few years but after I had a bra fitting the lady brought this for me to try.
“It still gives support but without the uncomfortable wired style.
“Highly recommend giving it a try.”
Marks & Spencers own technology, Flexifit™, is the key.
They say: "Flexifit™ “combines clean, minimalist silhouettes with innovative materials that feel luxuriously gentle on your skin.
“Bras with underwired cups provide extra support and uplift, while non-wired bralettes are an ideal choice for lounging.
“Our 360-degree stretch fabrics move with you for incredible comfort, whether you’re lounging or getting active.”
Another big busted shopper raved about the must-have bra saying it's “simply the best”, she added: “Omg these bras r the best iv ever had , being a big bust it is hard to find a good supportive bra.”
The bra comes highly recommended by a customer who is a size 42G. She says: “I have always worn underwired bras as a 42G, however, when they snap and start digging in you start looking at alternatives!
“I read the reviews and based on that I ordered it and I’m so pleased I did - it’s so comfortable, not having to constantly pull straps back up or adjust - it’s supportive and surprised me.
“Will be def ordering more.”
One happy shopper said: “These are extremely comfortable bras and do feel like a second skin.