For a fashion designer it is a unique task: dressing a woman who must be immediately recognisable from Antigua to Zimbabwe, visible from a distance, bright, dignified and immune to wardrobe malfunctions.
But the series of dressers who have worked with Queen Elizabeth II have helped her evolve a personal style that wins praise from unlikely quarters, including from a young French designer who worked for a decade with Jean Paul Gaultier.
"She has her own style and it works extremely well for her," Alexandre Vauthier told AFP. "It's really her DNA.
"She is the only person to dress this way, which makes her instantly recognisable."
The 86-year-old monarch's diamond jubilee this weekend marks 60 years of travelling, handshaking, and meeting global leaders as Britain's head of state.
On the biggest ceremonial occasions she appears in state dresses, jewels and even a crown, but humbler public engagements are no less challenging on the wardrobe front.
Her stylists, always British, must ensure that no garment is transparent, too tight or too short, and consider possible weather conditions -- including weighting her skirt hemlines to avoid embarrassment in a gust of wind.
For most of the hundreds of public engagements she carries out every year, the queen appears in a brightly-coloured outfit with a matching hat, neat handbag and sensible, yet elegant shoes.
Before any state or Commonwealth visit, her designers study meanings attached to colours, sleeve lengths and symbols in the country, both to avoid accidental offence and to be gracious to her hosts.
For her historic visit to Ireland in May 2011, the queen wore emerald green, the country's emblematic colour, and for a reception at Dublin Castle she sported a dress embroidered with no fewer than 2,000 tiny shamrocks.
On the first visit by a British monarch since the republic gained independence, her dress was a signal as powerful as the few words of Irish with which she began her keynote speech.
But those who have grown up seeing the queen as a distinguished older lady may be unaware of the glamour of her youth.
"Elizabeth in her youth was fun, vibrant, exciting and spontaneous," royal historian Kate Williams told AFP.
"And now we see a very different queen: she often is quite unsmiling; she's very fond of duty; she is very dignified."
In a photograph from 1954, the year after her coronation, the queen appears in a seductive tight-fitting white lace dress by Hardy Amies, her designer for some 40 years.
During the 1950s she wore a series of romantic evening gowns with ample silk and satin skirts, many of them by Norman Hartnell, who also created dresses for her wedding in 1947 and coronation in 1953.
In the 1960s, her dresses became closer-fitting and bolder; in 1969, meeting US president Richard Nixon, she wore hot-pink silk.
"The task of making clothes for the queen is not an easy one... not that the queen has been anything other than co-operative and professional in every respect," Amies, who died in 2003, said in a rare interview.
Amies "understood, as have other designers working for Her Majesty, that the wardrobe can make political statements," observed Country Life magazine, the bible of affluent rural Britons, in a special issue to mark the jubilee.
The queen's wardrobe is now the responsibility of designer Angela Kelly, the daughter of a humble dock-worker from the northwestern city of Liverpool, who joined her team of dressers in 1993 and became her personal stylist in 2002.
Kelly was behind the immaculate primrose-yellow ensemble the queen wore to Prince William's wedding to Kate Middleton last year.
She also created the white silk, satin and lace state dress with silver sequins the sovereign wears in her official diamond jubilee photographs.
Queenly fashion has inspired a raft of clothes and accessories issued for the jubilee, with corgis and tiaras in abundance as well as more subtle references to the queen's favourite colours.
Fashion iconoclast Vivienne Westwood has created a limited edition jubilee collection of dresses blending Britain's Union Jack flag with elements from the queen's own wardrobe.
The queen's grandson Prince Harry, along with many other commentators, called her outfits "impeccable".
Vauthier said: "She has her own look, and it wins her respect.
"She shouldn't change a thing."