LONDON — Thor, James or Frederick? Within seconds of hearing that Catherine, Duchess of Cambridge, had delivered her third child, a boy, social media erupted in celebration and speculation on Monday.

“My guess - Boy called Arthur or Jack,” one user wrote earlier in the morning. Others were a little less traditional in their views and opinions. “I’m telling you, it’s going to called Thor,” another tweeted.

But in Britain, the correct prediction of #RoyalBaby3's name may not only bring online applause. It can be worth real money.

Britain has long been home to one of the world’s most vibrant betting markets, which faces fewer hurdles than the more regulated American gambling industry. Bookmakers here frequently give odds on all sorts of things happening or not happening — including Brexit, the likelihood of nuclear war or the name of the next pope — even though sports bets are still the most common. Like many Brits, bookmakers tend to get most excited about one topic, however: the royal family.

As of Monday morning, London time, some of the names that ranked highest among British bookmakers were Arthur, Albert, Frederick, James and Philip.

The public is often left guessing about the name for days after a royal’s birth. In 2013, it took Prince William and Catherine, better known as Kate, two days to announce the name of their first child, Prince George, which only intensified the excitement both online and off.

While the bookmaker hype that spikes in the days before the announcement may strike some as bizarre, the common wisdom of thousands of Brits deeply committed to predicting the correct name has yielded some strikingly accurate results in the past.

When the second royal baby was born in 2015, the country’s leading betting companies ranked Elizabeth and Charlotte as the two most likely names. Her name was later revealed to be Princess Charlotte Elizabeth Diana, who will keep her place in line to the throne despite the revelation that the third child is a boy.

Britain’s obsession with the names of newborn royals extends far beyond its betting industry.

When George, who is third in line to the throne, was born, Britain celebrated with an array of official souvenirs. From fine china commemorative plates to souvenir mugs, the birth of the future king could not be ignored. The Royal Mint issued a special Royal Birth silver proof coin, giving away 2,013 silver pennies to babies born on the same day as Prince George.

Two years later, a popular restaurant franchise celebrated the birth of Charlotte by offering anyone named “Charlotte” free pizza. Those seeking free food were asked, of course, to bring along a valid form of identification to prove they had the same name as the royal baby.  The chain’s outlets around Britain advertised the deal, and hundreds of Charlottes walked into stores and called the restaurant to claim their freshly baked royal treats.

“A new royal baby and a free pizza, sounds like the perfect combination,” the company said at the time.

Indeed, William and Kate reportedly ordered pizza after the birth of their first child, Prince George.

Noack reported from Berlin.

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