She may be our future Queen, but in truth her tumbling mass of glorious, glossy locks has always been her crowning glory.

Glistening over her shoulders in flowing waves, or meticulously styled into an elegant updo, there is one consistent element to the Princess’s hair—it remains within a few familiar shades.

Catherine, Princess of Wales has always resolutely been a brunette. A dazzling, chestnut-hued brunette.

Not any more.

This week, in a bold style declaration for the autumn season, the Princess unveiled a striking transformation with a noticeably fuller and much blonder appearance.

A teaser of her updated hair color was seen earlier when Kate was noticed in the passenger seat of their family car heading to church near Balmoral last month.

But was it a trick of the light? Could it be just a sun-bleached reminder of summer holidays?

Well, it turns out it was neither. The caramel hue – believed to have been the work of Mario Charalambous, salon director at Richard Ward’s London salon – was unveiled in all its gleaming glory on an official visit to the Natural History Museum this week.

Catherine, Princess of Wales, has always resolutely been a brunette. A dazzling, chestnut-hued brunette – but not any more

Kate was spotted with noticeably lighter and brighter locks as she visited the newly renovated gardens at the Natural History Museum yesterday alongside Prince William 

The sunny new look – bronde, to use the fashionable term for a shade that is somewhere between brown and blonde – sets off a tan that tells of a summer well spent with her three children, Princes George and Louis and Princess Charlotte. It’s a shade many women strive to capture during the summer.

But what a lot of chatter it has garnered, particularly given it’s so thick and gleaming even though it was just a year ago when Kate released a video announcing that she was cancer-free after undergoing a course of preventative chemotherapy, a treatment that can cause thinning or hair loss.

Here, celebrity hair stylists reveal the secrets behind the Princess’s new lion’s mane.

The reason brunettes love to go bronde

Kate has made no secret of the fact she dyes her hair. But the down side comes in the summer months, especially if you have long hair, when exposure to the sun lifts the darker tones.

The solution, say those in the know, is to embrace a bronde shade, the fashionable way for brunettes to enjoy a sun-kissed look without looking washed out.

As top stylist Richard Ward says: ‘Bronde is a browny blonde and it’s a perfect after-summer colour – summer is holidays and sunshine and sand and sea and salt and wind, all great lifters of natural hair and coloured hair, and pre-coloured hair will lift up a bit more.

‘The very soft hair that grows near the top of the scalp lightens easily under the elements. And, of course, people often forget that with long hair, the ends might be three or four years old.’

Some hairdressers have suggested the Duchess of Cambridge has opted for a lighter hair colour is to hide the greys 

Going bronde is an effective way to hide the damage, bringing in caramel tones, along with the brunette undertones, to give a more polished look.

‘It can be difficult for a brunette to go blonde, because they might have to change their make-up and wardrobe, but bronde falls into a perfect mix of both so is more organic,’ says Richard.

Emilie Venturini, senior colourist at Jo Hansford Mayfair, adds that bronde is a great way to tackle greys. 

‘For many clients, moving several shades lighter can feel like a big change, which is why we usually advise easing into it gradually. It’s also important to note that as women mature, natural changes in skin pigment and eye colour can affect how hair colour complements their features.’

Why didn’t she lose hair after chemo?

As we know from Kate’s own conversation with a cancer patient during a visit to the Royal Marsden Hospital earlier this year, she didn’t even have to have cold cap therapy – a technique that helps reduce the risk of hair loss – during her own preventative cancer treatment.

Not everyone loses their hair after chemotherapy. Stylist Ed James, of Edward James London, says: ‘Everyone’s journey is different. Some shed early, some later, some not at all, and texture can change on regrowth.’

For some, a shorter cut reduces weight on the follicle, making it feel fuller. But Kate’s hair has continued to grow and looks the longest it has been in a long while. Colour is something Ed says he advises women to approach cautiously post-treatment.

Her hair glowed in the sunshine and was styled in soft waves that framed her face as she enjoyed the gardens 

Instead of losing her hair during chemotherapy, Kate’s long locks look more lustrous than ever 

‘I am always big on patch testing, even if a client has never reacted before. I also recommend having a strand test to see how the new hair behaves. Chemo can temporarily change hair diameter, porosity and melanin, which means colour may take faster, slower or differently than before.

‘The scalp is often more sensitive also, so I avoid on-scalp chemical services for about six months after treatment ends and I start with techniques that keep colour off the skin such as foils and highlights. Choose gentler colour methods on your hair and I suggest clients check with their oncology team before colouring.’

How come her hair is so thick? 

Kate’s locks may be long but, boy, does she know how to pump up the volume.

She has long been the queen of the bouncy blow-dry. But her new bronde tresses look even more voluminous than ever. So how can that be?

Celebrity crimper Sam McKnight knows a thing or two about styling royal blondes, as the man who was Princess Diana’s personal hairstylist from 1990 until her death in 1997.

‘When you make your hair blonder, it swells the shaft and it does make it look thicker.

‘It’s not going to give you more hair. It’s just going to give you the appearance of more hair.’

The Princess laughed and chatted with museum staff during her visit, tucking her new ‘do behind her ear as she listened intently

The mother-of-three opted for soft make-up to compliment her warm blonde hair

Failing that, there are always hair toppers, a small hairpiece that attaches over the top of natural thinning hair to give more volume at the root.

Is Kate trying to hold back the years? 

All manner of things can take a strain on a woman’s crowning glory, including stress, which as a mother of three – and one who has just gone through a gruelling period – Kate has borne aplenty.

As trichologist Iain Sallis says: ‘With three young children, stress, sleeplessness and nutrition stretched thin can all prolong recovery.’

Hair loss can, he says, lead to surprising changes when it grows back. ‘It often grows back with a ‘reset’ effect – curlier, straighter, or even a slightly different shade. Greys can appear more obvious if pigment production is disrupted. The regrown hair isn’t weaker, but as it’s new and shorter it can feel different to style.’

Kate doesn’t appear to have suffered hair loss. But her decision to go lighter in shade could have something to do with her age. 

Celebrity stylist Ed James explains: ‘As we age, skin becomes thinner and a little lighter, so the contrast between hair and skin shifts. Very dark, flat colour can start to look heavy next to a softer complexion.

‘I guide clients to soften and slightly lighten their colour, or to blend their greys rather than erase them.’