- At over 300 years old, Royal Ascot is one of Britain's most prestigious racing venues
- Top UK milliners inspired by spring, crafting fantastical hats with flowers and butterflies
(CNN)When it comes to dress codes, few horse racing events are as strict as Britain's Royal Ascot.
Don't even think about mixing with Queen Elizabeth II in the elite "Royal Enclosure" while wearing a headpiece with a base -- heaven forbid -- less than 10 centimeters wide.
That said, when Royal Ascot asked eight leading British milliners to design their dream hat, protocol didn't stop them crafting gravity-defying works of art.
Dramatic red butterflies, playful pink pom-poms, and towering sculptural twirls all feature in the millinery dream team's line-up.
Ahead of the five-day racing festival, which started Tuesday, we take a look at their designs.
Laura Cathcart developed a taste for millinery while growing up in an aristocratic horse racing family in Norfolk, on the east coast of England.
Her designs have been worn by Elizabeth Hurley in U.S. TV drama "The Royals."
"Decorated with red feather butterflies on a black woven straw base, this hat evokes the spirit of the Ascot social butterfly," Cathcart says of her dramatic creation for Royal Ascot.
"I wanted it to be feminine as well as chic and practical for watching the serious racing."
When Queen Elizabeth II needs a hat for a special occasion, she chooses Rachel Trevor-Morgan.
Whether it be her 80th birthday at St. Paul's Cathedral, the diamond wedding at Westminster Abbey, or meeting with U.S. President George Bush in Washington, Her Majesty has opted for a Trevor-Morgan hat.
"It's a sweeping straw hat lined with silk petals, each one hand-dyed, cut, and rolled," the English milliner says of her Ascot design.
"The effect of the different color tones adds a depth and beauty to this dramatic piece, creating the ultimate in femininity."
Perhaps the most famous of these was the oval, nude-colored fascinator worn by Princess Beatrice.
"This sculptured slice rises to the occasion in a rather contemporary yet feminine way," Treacy says of his Royal Ascot design.
Chambers has also created hats worn by model Kate Moss and singer Roisin Murphy.
"My hat features classic silk roses set against layers of crin, which create an out-of-focus geometric effect behind," Chambers says of his Royal Ascot design.
"It's inspired by my collection, Glass Gardens, which followed a visit to the glass flowers exhibition in Boston, U.S."
Veteran milliner to the stars, Stephen Jones has crafted headpieces for everyone from Princess Diana to 1980s pop singer Boy George.
Indeed, Jones even had a role in Boy George's band Culture Club's 1982 music video "Do You Really Want To Hurt Me?"
In a career spanning over three decades, Jones has worked closely with fashion designers John Galliano and Vivienne Westwood.
In 2009, Jones collaborated with the V&A Museum in London for the popular historical exhibition "Hats: An Anthology."
It's hardly the first time Edwina Ibbotson has designed a hat for Royal Ascot.
Kate Middleton's sister Pippa wore a minimal pink Ibbotson headpiece at the 2013 edition of the racing festival.
"I wanted to design a striking hat with clean lines and a touch of fun -- hence the pom poms," Ibbotson says of her 2016 Ascot creation.
"Boaters are normally a classic shape, but I have designed this piece to look very modern."
Before he was a London-based milliner, Harvy Santos was a professional ballet dancer in Hong Kong.
Today, his dramatic and elegant designs have appeared at the Royal Opera House and on the catwalk at London Fashion Week.
Philippines-born Santos says his Royal Ascot hat was inspired by birds and the centuries-old use of feathers in millinery.
"Spring is the time that birds -- and people -- will go dancing, displaying their finest feathers and plumage to mark a special occasion," he adds.
From boldly-printed caps, to vibrant panama hats, Laura Apsit-Livens' designs often appear like the pop-art version of millinery.
Though that doesn't mean she can't also turn her hand to intricate sculptural headpieces, when required.
"My signature piece is the Matador style, as I love the classic shape," the London-based milliner says.
"I wanted to have some fun with the piece for Royal Ascot -- to create movement and charisma with a sweetie-inspired duchess satin bow."