Prince Rupert (Ruprecht of Pfalz), The Great Executioner, a mezzotint

This huge mezzotint is a masterpiece from the early years of the technique. Prince Rupert (1619-82) had been taught the new process by Ludvig von Siegen in 1654. He improved the method of 'grounding', or initial roughening of the copper plate, by inventing a curved saw-like tool which he rocked back and forth across it. Presumably he chose to reproduce this painting (attributed to José Ribera, now in Munich) because its large areas of near-black tone displayed the excellence of his new ground.

Rupert was a nephew of Charles I (reigned 1625-49), and commanded the royalist forces during the Civil War (1642-48). He demonstrated the new technique of mezzotint to the Royal Society in London in 1661. To accompany John Evelyn's Sculptura, a history of printmaking published in the following year, he made a reduced version of this print (the 'Little Executioner'). Rupert and Evelyn chose to restrict knowledge of the technique to gentleman amateurs, so the description in Evelyn's book is deliberately obscure.

The forms and modelling of The Great Executioner are controlled with such confidence that it looks more like the work of a professional artist rather than an amateur, and it is known that Rupert employed the artist Wallerant Vaillant as his assistant. Whether or not Vaillant's job involved more than grounding and printing the plates, Rupert signed the blade of the sword with his own initials and a distinctive crown.