Still his position was most delicate, especially when the betrothal between the grand-duke Peter and Sophia of AnhaltZerbst (afterwards Catharine II.) was carried through against his will, and Elizabeth of Holstein, the mother of the bride, arrived in the Prussian interests to spy upon him.
From this time he was inseparably associated with Catharine in all important diplomatic affairs, though officially he was the subordinate of the vice-chancellor, Count Alexander Osterman.
To every Salon Houdon was a chief contributor; most of the leading men of the day were his sitters; his busts of d'Alembert, Prince Henry of Prussia, Gerbier, Buffon (for Catharine of Russia) and Mirabeau are remarkable portraits; and in 1778, when the news of Rousseau's death reached him, Houdon started at once for Ermenonville, and there took a cast of the dead man's face, from which he produced the grand and life-like head now in the Louvre.
Queen Margaret died in 1551; and a twelvemonth later Gustavus wedded her niece, Catharine Stenbock, a handsome girl of sixteen, who survived him more than sixty years.
He had his information from Newton's favourite niece Catharine Barton, who married Conduitt, a fellow of the Royal Society, and one of Newton's intimate friends.
In 1779 his bust of Moliere, at the Theatre Frangais, won universal praise, and the celebrated draped statue of Voltaire, in the vestibule of the same theatre, was exhibited at the Salon of 1781, to which Houdon also sent a statue of Marshal de Tourville, commissioned by the king, and the Diana executed for Catharine II.
Nevertheless he was deprived of the chancellorship and banished to his estate at Goretovo (April 1759), where he remained till the accession of Catharine II., who recalled him to court and created him a field marshal.
In 1654 Lightfoot had been chosen vice-chancellor of the university of Cambridge, but continued to reside by preference at Munden, in the rectory of which, as well as in the mastership of Catharine Hall, he was confirmed at the Restoration.