LONDON - France has the beret, while America has the humble baseball cap.

But Britain's love of hats is in a different stratosphere. Bowlers, baker boys, top hats, boaters, deerstalkers and countless ladies creations have been worn by royals and commoners alike through the centuries - a beloved tradition that will be in full force at Prince William and Kate Middleton's April 29 wedding.

Bookmakers are already betting on the color of Queen Elizabeth II's hat - odds are on yellow - and the designer making the princess-to-be's honeymoon headpiece. The salmon-colored tricorn hat that Princess Diana wore as she left for her honeymoon in 1981 spawned hundreds of copies.

"When people think of hats, they think of her majesty the queen," designer Philip Treacy, who is making some hats for royal wedding guests, told The Associated Press on Monday. "They're exciting hats to make, because hats and royal weddings are both about magic, happiness and a sense of celebration."

Theories abound on why Britain became a country of mad hatters - an expression referring to the Alice in Wonderland character whose loopy persona was based on the many milliners who suffered neurological damage as they inhaled the mercury used to cure pelts.

Britain's lousy weather might have contributed to the national obsession, but experts say it's the royal family that has kept it alive.

"Hats have long denoted status," says Oriole Cullen, curator of a Victoria & Albert Museum 2009 hat exhibit that has since gone to Australia and heads to New York in September. "Up until the 1950s, a woman wasn't even considered properly dressed unless she was wearing a hat and gloves."

The rebellious yet liberating swinging '60s spawned a variety of hair styles that - along with the cramped confines of the modern automobile - prompted a steady decline in global hat sales, Cullen says. Many milliners also blame John F. Kennedy - one of the first U.S. presidents not to don a hat - for hastening the demise.

In Britain, however, the tradition has stayed strong.

Royals have long been painted or photographed wearing hats - the Queen Mum had a special fondness for flouncy feathered creations, whereas her daughter has generally worn the same blocked style. Prime ministers and lawmakers, too, have worn top hats and tails at Oxford or Cambridge.

Britain is also home to the Henley Regatta, Royal Ascot and the Lords - posh rowing, horse racing and cricket events patronized by royalty where hats are de rigueur.

And then there are weddings and funerals.

Although the dress for William and Kate's wedding is not strictly formal - invitations allow men to wear suits - there will be a sea of ladies in hats among the 1,900 people invited to Westminster Abbey, much like the 1981 wedding of Prince Charles and Diana in St. Paul's Cathedral.

Designers say some women began placing their hat orders when the couple announced their engagement in November. Some have advised clients to be original, focus on their outfits, forget about the price and don't outdo the bride or royals.

Some creations by designers like Treacy, who made two hats for the Duchess of Cornwall when she married Prince Charles in 2005 and several other creations worn by Sex & the City star Sarah Jessica Parker, can cost more than 600 pounds ($1,000).

Treacy has been commissioned to do several of the hats for royal wedding guests but is tightlipped about his clients, who include the likes of Lady Gaga and Grace Jones.

He says his creations take anywhere from hours to weeks to make. Clients often come with sketches of what they're wearing or a swatch of fabric and explain other details, such as the type of event, what accessories they're wearing or even how they feel about hats.

Treacy calls hats "a cheaper form of cosmetic surgery" because they can transform facial proportions.

"When you meet someone, you meet their face," Treacy said. "It's the most potent part of the body to embellish."

Shirley Hex, a milliner who taught Treacy and has made hats for the queen, the queen's mother and Diana, agrees that choosing the right hat is key.

"The right hat can make a career," Hex told the AP, adding that she and other milliners were exhausted after Princess Diana's wedding. "But it also makes an outfit. Cars will stop and people will give up their seats to you if you have on a hat."

It's unlikely that royal wedding guests will suffer the ultimate fashion nightmare - seeing someone in the same hat - but it's still been the talk of the town.

Flight Lt. Al Conner, a pilot who helped train William and now flies alongside him on RAF search-and-rescue missions, is among 27 of the prince's military workmates who will attend the wedding. He says the airmen's wives have all been talking about the same thing: "What kind of hat is everyone else wearing."

Retail chains say the sales of some hats and fascinators - usually smaller pieces attached to a comb or headband - are down due to the recession. But in honor of the royal wedding - and to boost sales - London retailers will stay open for business on the public holiday. Associations have also encouraged their workers to don hats and fascinators during their shifts.

Specialty hat makers say they've seen a slight increase in sales ahead of the wedding.

"There has been no recession in Mayfair," says Nicholas Payne-Baader of the James Lock & Co. Ltd, a hat company in one of London's poshest areas that has supplied hats to the Duke of Edinburgh and Prince Phillip. "We're making about eight hats for the wedding."

Treacy's workshop in south London was abuzz with work Monday, although mum's the word on how many royal or celebrity hats he is actually doing.

"We are making beautiful hats for many of the guests to wear, and I believe in hats that make the heart beat faster," Treacy said.

Associated Press writer David Stringer contributed to this report from Anglesey, Wales.