In June 1761 George Montagu wrote Walpole, "Do you know Prince Rupert invented mezzotint? And prince's metal." Although Prince Rupert was generally credited with the discovery, he did not invent mezzotint; but he introduced it into England. Rupert is also credited with inventing "prince's metal," an alloy of copper and zinc. As the third son of Elizabeth of Bohemia and of Frederick V, elector palatine, Rupert was King Charles I's nephew. After 1640 he spent most of his time in England, becoming Commander-in-Chief of the royal forces. Under Charles II he was, among his many other duties and occupations, first lord of the admiralty from 1673 to 1679. He died in London in 1682.