The decision of who his future spouse would be, was sealed by his mother's close correspondence with the powerful Empress Maria Theresa of Austria, who had promised Ferdinand's parents the throne of the Netherlands, which had been returned to Austrian rule under the Treaty of Aix-la-Chapelle. This never occurred and, as a result, an alliance with the Austrian Empire was used to cement the two nations. This alliance was also encouraged by the Parmese Prime Minister Guillaume du Tillot, who had worked at Versailles and had been exiled by Louis XV of France due to his liberal ideas, which were not looked upon with much enthusiasm by those at Versailles.