One of the most notable achievements of the Duke's premiership was the arrangement of the King's marriage. The King had been betrothed to
Mariana Victoria, the
infanta of Spain, daughter of the Spanish king, in 1721, when she was just three years old, and the French king only eleven. By 1724, the king was fourteen but the
infanta was still a decade away from child-bearing age. Some felt that this was too long for France to wait for an heir. This was especially so because, if Louis XV died without an heir, it was feared that, armed with a hereditary right he had renounced when he became king of Spain,
Philip V de Bourbon, who had recently abdicated the Spanish throne, would ignore the
Treaty of Utrecht and claim the French throne, thus plunging France and Spain into conflict with the other European powers. It appears that by the summer of 1724, the marquise de Prie, and possibly also
Monsieur le Duc, were considering breaking Louis XV's engagement with the
infanta, despite the great offence this would cause Spain, and finding him a wife who might provide the country with an heir at an earlier date. By, at latest, the winter of 1724, replacement of the
infanta was being considered. Candidates included the Duke's sisters, especially
Mademoiselle de Vermandois. Mme de Prie was opposed to this choice because it would give the duchesse de Bourbon, Vermandois and the duke's mother too much influence. The duchess and Mme de Prie did not like each other. Furthermore, Fréjus was opposed to Louis marrying anyone from the Bourbon-Condé branch of the royal family. In April 1725, the seven-year-old
infanta was sent back to Madrid — Louis did not even say goodbye to her. A new candidate was sought urgently because, should Louis die with no heir, and assuming Philippe V of Spain did not seize the throne, then it would pass to the new
duc d'Orléans, son of the deceased regent; the
House of Orléans and the
House of Condé were rivals, so this would cast
Monsieur le Duc into the political wastelands. Prominent among these was a daughter of
George II of Great Britain. The prize was offered to her if she would consent to become a Catholic. However that would have caused great difficulties for her father, as he was occupying the British throne mainly because he was Protestant, whereas his rival,
James Stuart, was Catholic; he had to politely decline the offer of France to his daughter. Another prominent contender was the grand duchess, later empress,
Elizabeth of Russia. Others on the list included the
Princess Anne Charlotte of Lorraine; a princess of Savoy who was Louis XV's first cousin, and the
Landgravine Caroline of Hesse-Rotenburg. ==Marie Leszczynska==