The Mediterranean principality of Monaco owes much of its international profile to the Grand Prix, first held there in 1929, and its subsequent Formula One incarnation, and to Prince Rainier III's fairytale marriage to the Grace Kelly in 1956. Described as "The Wedding of the Century", the event enshrined Monaco's standing as the playground of the rich, while the private lives of the couple's three children, Albert II, the current ruler and Sovereign Prince of Monaco, Caroline, Princess of Hanover, and Princess Stéphanie of Monaco became staples of gossip and celebrity magazines throughout Europe.

Rainier's older sister, Princess Antoinette of Monaco, was a devoted aunt to Albert, Caroline and Stéphanie, but before they came along she had been a meddlesome presence in the Palace, while her private life also set tongues wagging. In 1943, after the Nazis replaced Mussolini's fascists as the occupying force, she took up with a German officer and intended marrying him until her grandfather Louis II intervened and decreed "this young girl will not marry anyone as long as the war continues."

After the war she began a relationship with Alexandre-Athenase Noghès, the Monégasque tennis champion whose father Anthony had been the founder of the Automobile Club de Monaco and the Grand Prix. She bore him three children out of wedlock, Elisabeth-Anne in 1947, Christian in 1949 and Christine in 1951, the year they eventually married, though they divorced in 1954.

Before Rainier met Kelly at the Cannes Film Festival in 1955 he had had a well-documented 10-year liaison with the French actress Giselle Pascal. The couple shared a villa in Saint-Jean-Cap-Ferrat, and considered marriage but, when Rainier ascended to the throne in 1949 on the death of Louis II, Antoinette began plotting a possible alternative to the succession.

Hoping to change the constitution that installed the eldest male heir as head of state, and become Princess Regent and have Christian replace or succeed her then childless brother, she began spreading rumours that Pascal was infertile. A doctor was said to have examined her and confirmed this, though she went on to marry the actor Raymond Pellegrin and bear him a daughter. But the whispers contributed to the end of Rainier's relationship with Pascal, and, for a while, made Antoinette persona non grata in the principality. She moved to neighbouring Èze, where she lived the rest of her life in a villa overlooking the Mediterranean called Le Bout Du Monde, surrounded by cats and dogs.

She was born in Paris in 1920, the daughter of Prince Pierre of Monaco (formerly Comte de Polignac) and Princess Charlotte, Hereditary Prin-cess of Monaco through Prince Louis II, who belatedly adopted Charlotte, the 20-year-old daughter he fathered with the cabaret singer Juliette Louvet in French Algeria, thus reinforcing the family's claim to the Monaco throne. Antoinette's parents divorced in 1933 and she and her brother spent most of their time with their grandfather in Monaco and Paris.

She was encouraged to interfere in the succession by Jean-Charles Rey, a lawyer and the then president of the Conseil National, who became her lover in the early 1950s and was her husband from 1961-74. Even if she still occasionally rowed with Rainier after his wedding to Kelly, he seemed to have forgiven her scheming. She got on well with Kelly and grew closer to her brother after his wife's death in a car crash in 1982. The following year, her third marriage, to the British ballet dancer John Gilpin, whom she had first met in Monte Carlo in the 1940s, also ended tragically when he died of a heart attack in London six weeks after the wedding.

Antoinette shared her brother's love of animals and established a sanctuary in Èze. She was president of Monaco's Society for the Protection of Animals. The rules of the succession were amended in 2002, three years before Rainier's death, and effectively sidelined Antoinette and her family's claim to the throne. Prince Albert is due to marry the former South African swimmer Charlene Wittstock in July. The current second in line is Caroline, Princess of Hanover.