They may have a 20-room mansion in Kensington Palace and a lavish country home retreat on the Queen's Sandringham Estate – but Prince William and Kate are down-to-earth people and just "like everybody else".
Fellow traveller Martin Katz, a famed Beverly Hills jeweller, met the couple while on holiday in Mustique back in 2008.
The royals are big fans of the ultra-private Caribbean island, which operates a no-fly zone, and regularly travel there to scuba dive, swim and play tennis, as well as relax at the Cotton House Hotel.
Celebrity jeweller Martin Katz met Prince William and Kate, pictured previously, on holiday in Mustique
"We went to a cocktail party at the Cotton House and William and Kate were there," Martin, whose wife is Kelly, told HELLO! magazine of their royal encounter. "I was at the bar ordering drinks and Kate came over and chatted for a bit. I told Kelly, 'Kate's been chatting me up, you have to be careful!' Then she invited us to come and meet William."
Kelly added: "Martin went to shake William's hand and dropped his glass of pink punch at his feet. It splattered all the way up William's white outfit, splashing him in the face. He said, 'Oh my, that was quite refreshing.'
"His mother would be so proud of him, he's such a gent. Kate's just beautiful. And they're quite the sportsmen. We went diving and they went very deep, more than 90ft. Our instructor said Martin and I weren't qualified to go on the shark dives they went on."
"She just couldn't be more gracious and talked to everybody who would talk to her," said Mr Katz of the Duchess
Given the complete privacy of the small island, it comes as no surprise that William and Kate, both 33, take the opportunity to dress down and blend in with other tourists.
"Kate looked very casual, she wasn't particularly wearing make-up, she looked lovely," Martin, who famously designed Kim Kardashian's wedding day earrings, added to People. "She just couldn't be more gracious and talked to everybody who would talk to her. It wasn't like she was working the room, but if someone wanted to speak to her, she was happy to speak."
"They were lovely and they couldn't be more present," he added. "I think what struck me was that they were human like everybody else, dressing to fit in like everybody else."
The last time William and Kate holidayed in Mustique was in January, just four months before the Duchess gave birth to the couple's second child Princess Charlotte. The royals similarly spent their first babymoon on the island when Kate was pregnant with Prince George in 2013.