Headgear made to look like clocks or huge sunflowers jostled with traditional-looking fascinators or wide-brimmed creations as the stands filled at the famous meeting.
Charles and Camilla swept onto the Berkshire course in the carriage procession with the Princess Royal, the King’s cousins, the Earl of Snowdon and Lady Sarah Chatto, and faces from the world of racing all joining the royal party.
Milliner Viv Jenner wore a striking hat made for the wearer to look through the brim with flowers at the centre made from feathers.
She said: “I designed this with the King in mind, it’s new beginnings.
“That’s why I decided to use the King’s silks, his racing colours of scarlet and purple with the gold represented by my accessories like my gold handbag.”
Bollywood actress Sofia Hayat wore a hat made from red paper roses and pheasant feathers designed by milliner Louis Mariette.
Mr Mariette said: “The inspiration for this was the new King Charles, so I wanted to make something that in some way was like a crown.”
Royal Ascot stalwart Tracy Rose, who has been attending the event for more than 40 years, is well-known for her striking self-made designs and said she had also been inspired by the new monarch.
She described the inspiration for her hat, made from a multi-coloured band of material twisted and twirled into an organic shape.
Ms Rose said: “It represents jockeys in motion, it’s the flash of colour and the twists and turns you get in horse racing.
“It’s made from a 12 foot-long piece of satin silk.
“A lot of people weren’t sure if the King was going to come or not but I’m really pleased to see him here.
“Obviously it’s going to take some getting used to, the late Queen is quite a difficult act to follow and was much loved.”