The Queen’s Own Hat Maker Explains The ‘4-Inch’ Rule at Royal Ascot

More than any other event of the year, Royal Ascot is really all about the hats.

And if you are lucky enough to be invited along to the Royal Enclosure (hello, Queen Elizabeth!), there are strict rules regarding what can sit atop your head.

“If you are in the Royal Enclosure, you must wear a hat with a fixed base of at least four inches,” British milliner Rachel Trevor-Morgan tells PEOPLE, adding, “I always encourage clients to go larger than smaller — it’s the one occasion where everyone is in hats and you don’t feel out of place going bold. In fact, you will regret if you don’t!”

Trevor-Morgan should know: She has been the Queen’s milliner since 2006 and has held the royal warrant since 2014. On Wednesday, the second day of the prestigious racing event, the Queen attended wearing one of Trevor-Morgan’s designs, a powder blue straw side-sweep hat with handmade pink silk roses that perfectly matched the floral print of the Queen’s Stewart Parvin dress.

“The Queen has a great hat style and absolutely knows what works for her,” says the esteemed milliner, who works from a small atelier in London’s upmarket St. James’s and has made more than 100 hats for the Queen during the last decade. “As with everyone, an Ascot outfit is a little more flamboyant and hat-focused. Her Majesty is known for her sense of color and always stands out.”

True to form, the 92-year old wore vivid canary yellow (and a new hat designed by her long-time personal dresser Angela Kelly) to open the races on Tuesday. But according to Trevor Morgan, more muted colors have been the trend for most of her clients this year.

Queen Elizabeth at Royal Ascot with Princess Anne on June 19, 2018.
Queen Elizabeth at Royal Ascot with Princess Anne on June 19, 2018.

“There have been a lot of pink, nudes and grays — very soft, beautiful colors,” she says. But more woman than ever are choosing big and bold designs, something Ascot obviously encourages with their 4-inch rule: “We have definitely noticed women going for a bolder silhouette with a more structured feel,” says the milliner.

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On Thursday — Ladies Day at Ascot — the Queen opted for another hat by Trevor-Morgan, this time a pink side-sweep style with handmade silk flowers and feathers — again paired with a matching Stewart Parvin outfit.

Queen Elizabeth at Royal Ascot on June 21, 2108.
Queen Elizabeth at Royal Ascot on June 21, 2108.

Founded by Queen Anne in 1711, the summer race meeting officially became a royal event in 1911 and is widely known to be the Queen’s sporting highlight of the year. The five-day event in Berkshire attracts racing fans from all over the world, celebrities and of course members of the royal family. On Tuesday, Meghan Markle made her Royal Ascot debut wearing an elegant, monochrome look by Givenchy, linking arms with Prince Harry as they walked around the grounds.

“Ascot is such an incredible celebration of hat-wearing, and everyone really pulls out the stops to look elegant,” says Trevor-Morgan, who says it’s not unusual for clients to plan their entire look almost a year in advance: “It is the most glamorous hat wearing event of the year and a thrilling week for us.”