LONDON (AP) — They’re good enough for the former Kate Middleton, but apparently not good enough for her husband’s grandmother, Queen Elizabeth II.

Fascinators — the delicate, whimsical pieces of headwear favoured by the young and posh in Britain and beyond — have been banned from the royal enclosure at Royal Ascot, one of the most exclusive events in Britain’s social calendar.

Organisers said Wednesday that those hoping to rub shoulders with the queen at the horse racing meet would have to stick to hats, no fascinators.

It’s the latest in a series of rules aimed at tightening the dress code at Ascot, where organisers have tried to push back against the proliferation of provocative outfits, outrageous accessories and revealing tops.

Other rules introduced or reinforced Wednesday include the requirement that women at the royal enclosure wear dresses that fall below the knee and that the men accompanying them must wear a top hat (gray or black).

The queen can wear whatever she wants, but the guidelines affect the royal enclosure, which usually includes a few hundred invited guests, not just the royal family.

Some of the rules — no bare midriffs or strapless dresses for example — fall in line with organisers’ attempts to roll back the nouveau-riche nightclub look, but fascinators are favoured by the highest reaches of the upper-crust.

Kate Middleton, now known as the Duchess of Cambridge, is a fan. So, too, are princesses Beatrice and Eugenie and other fashion-forward royals.

Nick Smith, Ascot’s head of communication, acknowledged that “there is an argument that some fascinators are formal.”

“But the very fact that there is that argument” was reason enough to ban them from the royal enclosure — where the queen gathers with the cream of British aristocracy to watch the races.

“Some fascinators have become so small that they’re nothing more than a hairband and a feather,” he added.

So did Elizabeth call up to say: “Off with their fascinators!” Smith laughed. “No, that doesn’t happen,” he said. “We set the rules.”

Still, he noted that organisers were in touch with the queen’s staff and he said it would be “unlikely that we’d put something in place that she’d be uncomfortable with.”

The next Ascot takes place in June.