The in-demand couple have previously been photographed at the exotic location with Kate’s family, but are thought to be enjoying some down time with their children; Prince George, Princess Charlotte and Prince Louis.
The Royal household is particularly concerned with guarding the secrecy of the family whilst on holiday, following previous breaches of privacy including a series of topless photographs taken of the Duchess whilst on holiday in France in 2011.
But paparazzi and Royal spectators are unlikely to snap any photos of the Royal family, due to strict regulations on the exclusive Caribbean island.
A source commented on the destination to Hello, stating: “Mustique is very exclusive and press and paparazzi can’t be within a certain distance from the island, which would explain why you only see long-lens, grainy shots of the royals.
“Security is really tight on the island.”
The insider noted the island’s security teams sail out to approaching vessels, and forbid day visitors from taking photos or brining cameras onto land.
Day visitors are also forbidden from accessing specific areas on the island, which are reserved solely for guests staying overnight and with proof of accommodation.
Commenting on the island, the insider said: “As soon as you dock, there are taxi drivers who you can hire to take you around and point out celebrity hotspots.
“We also went past the sloped runway where the private jets land.
“It was like something out of James Bond. It was surrounded by lots of trees – it’s almost like a secret, hidden runway.”
The island is also considered to be very safe, with the island’s security team being run by former Scotland Yard Chief Simon Humphrey.
Mustique’s official website says: “Every island visitor is registered with our security team before arriving on island by land, air or sea, whether staff, local islander or guest.
“This ensures the security team know who is on island at any one time.”
The island has hosted a series of Royal and A-list guest over the years, including visits by the Queen and Prince Philip in 1966, 1977 and 1985.
David Bowie also once owned a villa on the island, which he sold in 1994 for $5million.
Mustique is a small private island in the West Indies, which is part of Saint Vincent and the Grenadines.
The island covers 1,400 acres, and has several coral reefs and rich fauna which provides habitats for exotic creatures including tortoises, herons and iguanas.