By Roger Laing Cathy Nolan
August 27, 1984 12:00 PM

What is this mysterious attraction that Monaco and the movies have for each other? First a Prince Charming swept Grace Kelly off to reign over his beach-blanket Babylon, and now his daughter Stephanie seems to have thrown over the son of one famous European movie star for the son of another.

Until recently Princess Stephanie, 19 seemed on her way to a happily-ever-after life with car-racer Paul Belmondo, 21, son of Jean-Paul. But this month she was seen all over Monaco in a series of bathing suits that revealed much, and in poses that revealed even more about her feelings for Anthony Delon, 19. (He’s the son of Alain Delon, Jean-Paul’s rival for the sexiest grimace in French cinema.)

The pair was seen hand in hand at poolside, nuzzling at night spots and zipping around the Mediterranean on a sea scooter. Said one of the pool staff, “They look like a couple in love.” But an acquaintance disagreed. “It’s a strong friendship. The Princess isn’t stupid. If it was a real love affair, it would be hidden.”

The sudden switch in Stephanie’s affections could not possibly be pleasing to Prince Rainier. It was Belmondo who nursed a distraught Stephanie back from the 1982 car crash that killed her mother and left her with a fractured neck. He was welcome at the palace and marriage was rumored.

While Belmondo is a quiet young man who has worked his way up the racing ladder with his father’s backing (Paul has moved from Formula Renault to Formula Three this year), Delon is a moody nightclub fixture estranged from his dad. In January 1983 Delon was arrested in a stolen BMW with a gun. He got a suspended sentence after the defense portrayed him as a lost boy who’d seen too many of his father’s tough-guy movies. Now young Delon is designing leather clothing—although his father is suing to make him quit using the initials “A.D.” on his jackets.

As for his fling with Stephanie, Delon may simply be seeking career-boosting publicity—or even a form of competition with Belmondo, who has been cast in the press as Stephanie’s white knight. Belmondo and Delon apparently met her at around the same time and at the same Paris nightclub, the Elysées-Matignon. Delon had her out all night on a 1982 date, but to her disappointment, never called back. Now Delon is pursuing Stephanie, although she reportedly called Paul at his mother’s home near Cahors to assure him that she had not been unfaithful. “Just because Princess Stephanie has been photographed on the beach with another boy,” says palace spokeswoman Nadia Lacoste, “doesn’t mean she’s changed her life.”