Princess Grace Patricia née Kelly may have grown up in East Falls, near Philadelphia in Pennsylvania, but she ended her life as the personification of Monaco, Le Petit Province, down the French Riviera from Nice.

Her Serene Highness is still revered unreservedly in Monte Carlo, which might explain the royal family’s frosty reception to Nicole Kidman’s new film Grace of Monaco.

Critics also panned the biopic, which stars Tim Roth as Kelly’s royal husband, when it opened at the Cannes Film Festival last month.

The Hollywood star gave up acting after her marriage to Louis Henri Maxence Bertrand Grimaldi (Prince Rainier III), who even banned her films in Monaco.

She died at the age of 52, the day after suffering a stroke while driving her Rover 3500. It is claimed she was driving on the same stretch of road seen in the classic Cary Grant movie To Catch A Thief.

The actual spot of the accident on the Moyenne Cornice mountain road is marked by a small stone bearing the date Sept 14, 1982. Nobody knows who put it there.

After his father Prince Pierre de Progniac died, Prince Rainier III allegedly inherited a treasury that was virtually empty. Gambling accounted for nearly all the principality’s revenue.

On his own death in 2005 – after the Princess Grace factor had kicked in – it accounted for just three per cent.

The princess put Monaco on the map. One square mile became synonymous with opulence and glamour.

By becoming a Monégasque, she romanticised and became the unmistakeable face of the principality. Everything changed following her much-needed PR, and tourists and their money followed in her wake.

To commemorate her enormous influence, you can now follow the two-hour Princess Grace Walking Trail, which takes you to 25 locations associated with her life. The Chémin des Pecheurs waterfront, beneath Jacques Cousteau’s Oceanographic Museum, is the obvious starting point.

There, on April 12, 1956, a beautiful lady stepped off a luxurious boat provided by the richest man in the world.

She wore an elegant, navy-blue coat and large white organdy hat and carried a poodle called Oliver so that her husband-to-be could not kiss her.

Protocol had to be observed: there was no embracing before the big day, although the fact that Princess Caroline was born nine months and four days after their marriage implies the couple had plenty of passion for each other.

A band played The Star-Spangled Banner as red and white carnations fell from a seaplane flying low over the Mediterranean – a floral tribute arranged by Greek billionaire shipping magnate Aristotle Onassis.

He also provided the yacht Deo Juvante II for the short journey into Monte Carlo’s Port d’Hercule where, after acknowledging the applause of her subjects-to-be, the iconic figure ducked into a green Chrysler and was whisked off up the hill to the royal palace and into history.

The launch is now taking tourists around the Galapagos Islands.

“The eight-day trans-Atlantic voyage from New York’s Pier 84 on the liner SS Constitution gave everyone time to paint the palace,” said my guide Beatrice Projetti as we walked up towards the Old Town.

Protocol had to be observed: there was no embracing before the big day

She provided a potted history lesson. The couple met at the Cannes festival while Kelly was on a photo shoot for Paris Match and the prince took her to the zoo for their first date, although their first public appearance was at a glamorous charity event at New York’s Waldorf Astoria Hotel.

We watched the changing of the guards outside the palace.

“The princess gave parties for the local children. I remember going one Christmas. She gave me a clock,” said Beatrice, who went to school with Prince Albert.

“She did so many good things. The Red Cross HQ and her crêche are on the walking tour. She founded AMADE (the World Association of Children’s Friends NGO) and a garden club to decorate old people’s homes.”

The princess also revived charity balls. In 1950 she opened Le Grill – one of Monaco’s seven Michelin-starred restaurants – on the eighth floor of Hotel de Paris, and held her 20th wedding anniversary in its wine cellars.

She chose the Hermitage Hotel for her 40th birthday party, attend-ed by her former Hollywood companions Elizabeth Taylor and Richard Burton.

We came to St Nicholas Cathedral, where the couple were married and are buried. Flowers are still left regularly in homage to her memory and engraved into marble are the words Gratia Patricia.

An exhibition dedicated to the former ruler called The Grace Kelly Years, Princess of Monaco has been on a world tour since 2007. From June to October 26 it will be at the Het Loo Palace in the Netherlands.

On display are the dresses Kelly wore in the film High Society and to collect her Oscar for Country Girl (1955). As well as hats, broaches, bracelets and necklaces, there is her 12-carat, emerald-cut diamond engagement ring and signature Kelly Hermes bag.

There are two statues of the princess in Monaco. One is by the Forum near Larvotto Beach and the other is in the memorial rose garden near the heliport.

As the Parcour Princess Grace tourist trail takes you down Avenue Pasteur and down Boulevard Belgique, other stops include the theatre, the hospital and the Japanese garden where she planted two cherry trees.

“Everyone knows what they were doing when she died,” said my guide sadly.

“Our princess is eternal and much missed. She was an extraordinary woman. She owned her own London taxicab!”

One of the strangest locations on the sightseeing trail is behind the Grimaldi Forum cultural centre. It is the Promenade Golden Foot, which the princess opened. Football legends like Maradona and George Best left their foot-prints in the pavement by the Mediterranean Sea.

Princess Grace made a far more lasting impression.

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