Charles and Camilla on secret honeymoon

Prince Charles has taken his new wife on a secret honeymoon cruise courtesy of a Greek billionaire.

The royal couple are expected to tour the Greek islands over the next few days aboard a yacht owned by billionaire tycoon Spiros Latsis, one of the world's richest men.

Charles, fresh from a solitary break at an isolated Romanian monastery, is expected to join the Duchess of Cornwall on the cruise today.

It is understood she flew out earlier this week on a private jet, while Charles headed for his "isolation" break.

Dr Latsis leases some of his private fleet for up to £200,000 a week but it is not known if Charles is opening his chequebook to pay for the private hire.

In the past Charles has been widely criticised for accepting free cruises from Mr Latsis's late father, controversial shipping tycoon John, who repeatedly gave the prince free holidays with both Diana and Camilla aboard one of the world's largest private yachts, the Alexander.

Prince Philip was reportedly infuriated by Charles's refusal to limit the largesse that he routinely accepts from the rich. On at least one occasion Philip is said to have criticised him in front of other members of the royal family after Charles went on a two-week jaunt on the Alexander with 22 people, a trip that would have cost him £500,000 had he paid for it.

Self-styled "Captain" John Latsis was the son of a peasant fisherman , born in poverty, who battled his way to success and enjoyed letting people know it.

The Captain took particular pleasure in his relationship with the British royal family, lending them the Alexander, a helicopter and his private jet.

Some critics suggested that he paid £19 million for Bridgewater House, his London home, because its immediate proximity-to St James's Palace gave him access to Prince Charles. His son Spiros was briefly caught up in controversy last year when it emerged he had entertained EU commissioner José Manuel Barroso on his yacht, but prefers to stay out of the limelight.

Clever, discreet and determined to succeed in his own right, Spiros excelled at school and university and shone from the moment he entered his father's business.

He never succumbed to the temptations of the playboy life that claimed the heirs to many other shipping fortunes, instead immersing himself in the running of the Latsis empire.

That devotion to duty has paid rich dividends. Under his stewardshipthe business has diversifiedand prospered, particularlyin the banking sector.

His greatest success has been the establishment of EFG Bank Group, a Swiss-based investment house catering for the very rich.

Spiros, who has a PhD from the London School of Economics, also masterminded a £300 million investment in a Greek oil refinery and set up PrivatAir, an aviation company which hires private jets.

He is estimated to be worth between £2 billion and £3billion with the Sunday Times rich list ranking him the world's 11th richest man.

Charles and Camilla are understood to be aboard one of Mr Latsis's smaller yachts, possibly Spiros's personal cruiser the Dumara, as the Alexander is now in dry dock.

The couple are accompanied by a number of friends but are due back ahead of Monday evening when they will be at a theatre gala.

A well-placed source said: "The Duchess of Cornwall, accompanied by friends, is already aboard and enjoying her holiday.

"She is expected to be joined by the prince today and they will enjoy a few days cruising the Greek islands.

"They enjoy cruising and it is the perfect escape after the stress of the wedding."