Monaco succession crisis of 1918 of this event, pursuant to the clauses of the treaty of 17 July 1918." The French government at the time was still the Vichy regime. Louis II died on 9 May 1949. The Principality of Monaco passed to his grandson, Rainier III. In the absence of an heir male, the ducal titles of Valentinois and Estouteville became extinct in French nobiliary law. Before Rainier III married Grace Kelly in April 1956, he notified the French government of his plans; the French ministry of foreign affairs replied with a message of official congratulations. Count Louis de Causans is suing the French
Rainier III, Prince of Monaco have been romantically involved with his second cousin, Princess Ira von Fürstenberg, a former actress turned jewellery designer, who is also a Fiat heiress and the former sister-in-law of fashion designer Diane von Fürstenberg. Princess Ira, like him, is a great-grandchild of Lady Mary Victoria Hamilton, the Scottish-German wife of Prince Albert I of Monaco, though by Lady Mary's second marriage. After Grace's death, Rainier refused to remarry. Rainier established a postal museum in 1950: the Museum of Stamps and Coins, in Monaco's Fontvieille district by using the collections of the Monegasque princes Albert I and Louis II. The prestigious