You may not have heard of Marlies Dekkers, but the Dutch lingerie designer is a bit of a legend in the underwear world.

After becoming frustrated with frumpy lingerie, Marlies set up her business from her bedroom 20 years ago, and has since elevated the bra and pant into an art form. Her cage-like Dame de Paris bra designs enjoy cult status, with a celebrity following that counts Lady Gaga, Rihanna, Victoria Beckham, Mila Kunis and Dita von Tees amongst its fans.

Now, with a pop up store in Harrods under her belt and her range available online from the luxury retailer, Marlies is bringing her own brand of fashionable lingerie to the UK (we've tried her bras, and they look great). No one is better placed to talk underwear, so we asked the designer for her rules for buying stylish underwear that actually fits .

Shape is just as crucial as size

So many women don’t wear the right size bra, (the under bust and cup size are the parts of the breast they need to check) but the shape is just as important, as different shapes work for different breasts. When you are eighteen, your breasts are perky and follow a certain line away from the body – it’s quite high and rounded, and as you get older that line gets lower and less rounded. A soft bra follows the shape of the breast exactly, whereas a moulded cup reshapes the line of your breasts with the wiring. So if you put on a moulded cup, it gives you back the breasts you had when you were eighteen! But it’s best to try on different bra shapes and see what you prefer – some women find a soft moulded cup as it’s a little more comfortable.

There is no such thing as the ‘perfect cleavage’

In my opinion, the only “perfect cleavage” is one that gives a woman sparkles in her eyes! But for that to happen plunge or push up styles need to fit and shape your breasts properly. I put numbers on each bra’s hang tag that refer to shape as well as size, so once you know your number you can easily find a bra that works for you.

There is no ‘right time’ to shop for lingerie

All women have different right and left sized breasts, and with your changing hormones, their size can often fluctuate. But a good moulded cup bra (not a soft one) can cope with changes in breast size. My bras still fit women who have had breast cancer and a small part of their breast removed from surgery. If your weight or breast size really fluctuates a lot, then a moulded cup is the best shape for you.

Don’t hide your breast size

I’m always asked what the best bras are for small breasts, but it depends what you want. If you are happy with your size ( my sister has a small B cup, but she is very proud of them!) then go for a soft bra and relaxed fit. If you are worried they are too small, then go for a push up – or double push up – to get a cleavage.

A lot of woman with big breasts think they have to wear a minimiser – but the breasts have to go somewhere! With a minimiser your breasts are squished downstairs, so you look thicker, like you have an extra layer of flesh under your bust – not very flattering!

I always recommend women with big breasts to wear a moulded cup bra – you get your full shape back which makes a huge difference and it makes you looks slimmer. People didn’t believe me until they try it – but now more and more women are taking my advice and being proud of their breasts.

How to shop for lingerie