It’s akin to feeling as if your best friend, who knows all your secrets and has witnessed your highs and lows—standing with you before an unyielding mirror in just your underwear—suddenly vanishes. A gut punch just when every bit of strength and confidence is needed to face the world. A confidante who calms your fears, bolsters your spirit, and, most crucially, always gives you her honest opinion.

Learning that the Princess of Wales’s personal stylist, Natasha Archer, is departing after 15 years to launch her own venture must resemble experiencing a breakup. Who will be there to support me now?

Since joining the Royal household as a junior assistant in 2010, the same year William and Kate announced their engagement, 37-year-old Natasha ‘Tash’ Archer has been at Catherine’s side for pivotal moments. She discreetly brought in dress options when the new mother appeared on the steps of St Mary’s Hospital with baby George and accompanied the princess on official trips abroad to Norway, Pakistan, Bhutan, and Canada. Together, they’ve grown more assured.

The blue dress by Issa worn for the engagement announcement reflected Kate’s psyche at the time: modest, sticking to what she knew and loved. But this week? The metamorphosis from ordinary to outstanding reached a crescendo when Catherine wore a champagne Dior ‘Bar’ jacket and chiffon skirt to greet President Macron and his wife, Brigitte.

The Princess of Wales’s personal stylist, Natasha Archer, is leaving her side after 15 years to set up her own business

This was the first time she has been seen in the French couture label and, boy, did she pull it off. The original Bar jacket, designed by Monsieur Dior himself in 1947, would have required its wearer to don a corset. No need for that with Catherine, who has made Dior’s Corolle silhouette – the name means the wearer resembles an upturned flower, with etiolated limbs, like stems – her trademark. Just, wow!

Tash has honed Catherine’s signature style, which isn’t remotely edgy. You never see the princess in a short, sexy shift, a la Diana. There is nothing too revealing. Of course, wearing a hat requires hair to be up or back, but Kate knows we all want to see her hair flowing. Can I kneel in it? Can people see my face under this hat? The conversation between the future queen and her dresser will have been intimate. It’s easy to see how they became close friends, often seen giggling together at boring sporting events.

The job of a stylist is far from easy, especially if you are dressing one of the most photographed women in the world. A stylist needs to have good relationships with designers – the two have remained loyal to Sarah Burton, who designed the princess’s wedding gown while at McQueen, and made the crimson caped gown she wore to the official State Banquet on Tuesday night – as well as impeccable taste, an ability to push, reassure and coax. 

The metamorphosis from ordinary to outstanding reached a crescendo when Catherine wore a Dior ‘Bar’ jacket and chiffon skirt to greet French President Emmanuel Macron this week 

In May, the princess wore a spring yellow dress by Emilia Wickstead and a hat by Philip Treacy at her first Buckingham Palace Garden Party since her cancer diagnosis

Will the fabric crease, will the skirt be easily lifted by a strong breeze, is it culturally appropriate, does the bodice work with a sash, so many brooches and, most important of all, is it comfy? Hundreds of micro decisions go into every public appearance that, if you get it wrong, social media will dissect and magnify.

Catherine will have been nervous on so many occasions, not least appearing in public for the first time after her treatment for cancer. Natasha will have acted as a counsellor, someone to lean on, as well as being able to adapt to the princess’s shape and mood.

Catherine announced earlier this year she wanted the focus to be on her work, not what she is wearing, but I think the choice of Dior shows her silently flexing her sartorial muscles. A French label was worth more than any number of speeches about the Entente Cordiale. While Kate depends on and trusts Natasha, she has never been a pushover when it comes to getting dressed. When she posed for British Vogue in 2016, even the magazine’s super bossy stylist, Lucinda Chambers, was unable to persuade her into anything too princessy. 

There have been very few slip ups. Only the green Vampire’s Wife dress worn for the first official portrait with William springs to mind – too Quality Street wrapper, too droopy. A few too many brown, scratchy tweed coats. 

But over the past year, when she must have had an inkling Natasha was leaving, Kate has come into her own. The choice of a pastel Victoria Beckham trouser suit for a British Fashion council event in May was inspired.

Natasha is married to Chris Jackson, who photographed the King and Queen for their 20th wedding anniversary portrait and was given access behind the scenes at the Coronation. They have two children. Perhaps tired of always being the bridesmaid, she plans to open her own consultancy. My guess is that Catherine will see this as a scary-at-first opportunity to spread her wings even wider, moving away from the safe and the Sloaney and towards wearing more couture.

Natasha is married to Chris Jackson, who photographed the King and Queen for their 20th wedding anniversary portrait. They have two children 

Because, once you have worn Dior, it’s hard to settle for anything less: the fit, the fabric, the colour. Once Kate becomes queen, the role of her personal dresser becomes all-consuming, with no time for a personal life. The late Queen Elizabeth of course had the devoted Angela Kelly, and relied heavily upon Scottish couturier Stewart Parvin, who told me the Queen would stand in her underwear in front of a full-length mirror, completely without vanity. It was her job to always look her best, to be reassuring, cheery and constant.

Kate is now making that shift, from real woman to fantastical icon. To lose Natasha now is tough, but I think it will be the making of Kate as she shifts gear and evolves a stateswoman. All eyes will be on what she wears at Wimbledon on Saturday, and of course whom she hires next. The arm bands are well and truly off.