In 1653, he obtained high office in the kings household and in 1654, he was ambassador extraordinary at the election of Pope Alexander VII.

He and the Cardinal cultivated relationships with German nobility, including Franz Egon of Fürstenberg, prime minister of Cologne, and his brother Wilhelm.

[3] With their help, Hugues was instrumental in forming the league of the Rhine, by which Austria was cut off from the Spanish Netherlands, and, as minister of state, was associated with Mazarin in the Treaty of the Pyrenees (1659), which secured the marriage of Louis XIV to the infanta Maria Theresa of Spain.

[2] At the cardinals dying request he was appointed his successor in foreign affairs, a position he held from 3 April 1663 to 1 September 1671.

[2] One of his sons, Artus de Lionne, became a missionary of the Paris Foreign Missions Society, and was active in Siam (modern Thailand) and China.