They are expected to spend more than £322 million ($401 million) on accommodation, food, shopping and attractions.
Anna Bloomfield, an Australian in her forties, has already arrived in London ahead of the ceremony.
She admires King Charles "for everything that he has had to endure just being a part of the royal family".
Bloomfield has packed a tent for her own endurance test -- waiting in all weathers to secure a prime spot to watch the royal couple pass.
Kathryn, a 54-year-old executive assistant from Toronto, Canada, can't wait to experience the "pomp and ceremony which the British are famous for".
"He has already shown his desire to modernise, streamline, cut excess and make the modern day royal family resemble the cultural and religious make-up of Britain today," she said.
"He is open-minded, defends the environment, he lives in his time", added Decker, who praised the "humanity" of Charles' charity works.
Demonstrating the coronation craze, European travellers' internet searches for flights to London over the coronation weekend are 65 percent higher than for the same weekend in 2022, and 105 percent for hotels, according to data from US search engine Kayak.
And "the French seem to be the most interested", added the company, with Americans making up the bulk of visitors from outside of Europe.
The coronation's boost to the country's pulling power is beyond measurement, according to Patricia Yates, director general of Visit Britain, which promotes tourism.
"Millions and millions of people will see the coronation on their television set and hopefully will be inspired to come and see London to see the royal residences... and to see special exhibitions that are being held," she told AFP.
They include royal dresses at Kensington Palace and special waxwork statues at Madame Tussauds, while hotels and cafes will serve special coronation "afternoon tea", and many shops will sell souvenirs bearing the image of the royal family.
Around 600,000 people visited Buckingham Palace after William and Kate's wedding to see the bridal gown on display, recalled Yates.
Added to the mix, there is also "a real appetite for international travel, and an appetite for experience" following Covid-19.
"And what better experiences than... seeing a monarch being crowned," she added.
