A quarter of a century after she was killed in a tragic car crash, Grace Kelly, the American screen goddess, continues to extert a powerful fascination in Monaco and beyond. The woman for whom a fairytale seemed to have come true when she married Prince Rainier was an icon of the 20th century: her death provoked a Princess Diana-style wave of mourning and her influence can still be felt in the obsessive interest in the doings of her children, Princesses Caroline and Stéphanie and her son, Prince Albert.

It is Albert who greets me in the picturesque palace in Monaco for a rare interview. With his sisters he has been helping to orga-nise a special summer exhibition to commemorate the 25th anniversary of his mother’s death. It opens at the Grimaldi Forum in Monaco in July and includes many ravishing pictures of Kelly, items of clothes and jewellery as well as love letters, snapshots and home movies that are “a nice insight into different aspects of family life”.

Kelly’s marriage to Rainier in 1956, a combination of European aristocracy and Hollywood stardust, helped to turn the seaside enclave wedged between Italy and France – Somerset Maugham famously called the region “a sunny place for shady people” – into a magnet for finance and tourism. Albert says his mother made a “huge” contribution to promoting Monaco internationally, but it is in her private rather than her public role that he prefers to remember her. Kelly loved her role as a mother of three, he says: “She put a lot of herself into being a mother and that took over from any other aspect of her former life or the fact that she was a princess and that she had official duties.” It is only now that he is beginning to realise the impact that her sudden and early death had on the family: “I think we underestimated it.”

Kelly met Rainier at the Cannes film festival of 1955. Rainier, a keen stamp collector and lover of vintage cars, showed her round his gardens and private zoo. Romance blossomed and captured global attention: the MGM studio paid for Kelly’s wedding dress, did her hair and even won the rights to make a documentary about the “wedding of the century”.

Albert, who was 24 when she died, remembers listening in fascination to his mother talking about films: “I would ask her ‘what was it like on that set?’, ‘what happened there?’ We met Alfred Hitchcock several times. Cary Grant was also a great friend of hers and a frequent visitor here.”

When they watched films at home “it was always kind of strange to see her on the screen and to turn your head and she was there”. His favourite is Rear Window. “I’d mention High Noon also, which is one of the great classic movies of all time.”

Kelly did not say explicitly that she regretted giving up her film career for royal formality, but her son sensed she was restless: “At different times she felt that she would have liked to do something more and that she didn’t finish what she had set out to do.”

The car crash that claimed Kelly’s life on a hairpin bend on the Corniche above Monte Carlo in 1982 cruelly marked all her loved ones. Rainier was devastated by the loss and channelled his grief into public works before his death ended a long illness in 2005. He was buried next to Kelly in the cathedral down the road from the palace.

Things were hard, too, for Albert. His last memory of her is from shortly before the crash. “She had come into my room to try to get me out of bed,” he says. “I was still having breakfast when I heard the news from my father. It is a devastating moment, to lose a parent, especially a mother, at any age.”

It was Stéphanie, however, who suffered most. She was with her mother in the car and escaped with neck injuries when it plunged over the cliff onto the road below. Albert said Stéphanie had suffered from posttraumatic stress disorder. “She could have talked to someone in that medical field,” he says. “But she didn’t want to. It is hard to force somebody to do that kind of thing.”

This, he adds, explained her “difficult years”. Stéphanie, the “wild child” of the clan, tried her luck as a swimwear model and a pop star and had relationships with unsuitable men, including a circus performer. She, too, has blamed her erratic behaviour on the car crash. “Nobody can imagine how much I’ve suffered and still suffer,” she once said.

Not that Caroline, her elder sister, fared much better in love. She shot to fame by stripping off at the Monte Carlo beach club as a teenager and by defying her parents to marry Philippe Junot, a playboy 17 years her senior who sold their honeymoon snapshots to the press.

After divorcing him, she married Stefano Casiraghi, a young Italian businessman who died in a powerboat accident off St Jean Cap-Ferrat in 1990, prompting talk of a “curse of the Grimaldis”.

She has since married Prince Ernst August of Hanover, a cousin of the Queen, but hopes for the centuries-old Grimaldi dynasty now rest on the three children she had with Casiraghi: Pierre, Andrea and Charlotte. That is, until Albert produces a legitimate heir. He has acknowledged having two children: Jazmin, a 16-year-old Californian whose mother he met when she visited Monaco as a tourist, and Alexandre, the five-year-old son he had with a former Togolese air hostess.

Jazmin, he said, had been to see him in Monaco. “I’ve received her,” he says. “Everything is fine.” The young Alexandre and his mother have been installed in a villa in the port of Villefranche, not far from Monaco. Neither can make any claim on the throne – the constitution does not recognise heirs out of wedlock – and courtiers are increasingly eager to see Albert settle down to ensure the succession.

Albert, however, may not yet be ready.

Having previously expressed an interest in actresses and supermodels such as Sharon Stone and Claudia Schiffer, for some time recently he has been dating Charlene Wittstock, a South African Olympic swimmer. But when asked if there was any prospect of a wedding announcement he says: “No. Nothing. No plans right now.”

Albert says he felt a “great responsibility” looking after his mother’s legacy and that helping to put together the exhibition has brought back all sorts of memories of her. “I hadn’t seen some of her dresses for years,” he says. “With my sisters we were saying, ‘Remember when she wore that on that day?’ So it was odd. Personal belongings, some of her pressed flower paintings, col-lages, they also bring back memories. There’s something of her life and of her personality in everything.”

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