"Have you ever seen any place in the world more wonderful?" swoons Grace Kelly, after whizzing round a hairpin bend above Monaco in an open-top car with Cary Grant, in the 1955 classic "To Catch a Thief."

The same hillside road would cost Kelly her life on September 14, 1982, yet 30 years on the Hollywood actress-turned-princess still symbolises the tiny Mediterranean principality she helped turn into an international jet set Mecca.

"'To Catch a Thief," is the best advertisement we ever had," said Monaco's head of tourism Guillaume Rose, who plays the scene from Alfred Hitchcock's romantic thriller whenever he wants to introduce the principality abroad.

The blonde beauty met her future husband Prince Rainier almost a year after shooting the film with Hitchcock, during a visit to the palace set up while she was in the region for the 1955 Cannes film festival.

They wed in 1956, Princess Grace cut short her Hollywood career aged just 27, and threw herself into her new role.

"She had been a professional actress, she was a professional princess," said Louisette Levy-Soussan Azzoaglio, her personal secretary of 19 years. "The princess polished up Monaco's image" from the moment she stepped off the boat.

"Though she had turned a page on her career, she was a loyal friend," receiving a regular stream of glamorous visitors from Grant and Hitchcock to Frank Sinatra, Ava Gardner, Liz Taylor or Richard Burton, Azzoaglio recalled.

"Grace brought the entire world here," said Rose. "The princess symbolised culture, she injected life, and a touch of fantasy that offset Rainier's extreme realism."

"She belonged to another world," agreed Azzoaglio. "People sometimes described her as cold and distant, but she was full of enthusiasm, and very curious about the life she was discovering."

"She was dedicated to what she saw as her role as a kind of mother to the Monegasque people," setting up charities and kindergartens, she recalled. "When she died, Monaco was overcome with sadness."

Three decades after her tragic death aged just 52, "the princess' image is still as strong as ever," said Rose. "She stood for a time of absolute prosperity, a blessed era in every sense."

An exhibition about the princess' private life, launched in Monaco in 2007, has since travelled around the world, to Paris, Moscow, Rome, London, Sao Paolo, Toronto and in the town of Bendigo in Victoria, Australia, where it smashed attendance records.

The principality continues to play on the image of Grace, stunning in her 1950s gowns, most recently in July at an evening to woo new business leaders in Capri, which was dotted with pictures taken of the style icon in 1959.

Monaco's royal family will mark the anniversary of her death on Friday with a private ceremony in a chapel of the palace, but her son Albert II will join in a public screening Saturday of "To Catch a Thief", in a newly remastered version.