Carthusian Martyrs of London were canonized by Pope Paul VI in 1970. There is a memorial plaque at Charterhouse Square. A private commemoration ceremony takes place each year at the Carthusian martyrs plaque on 4 May, the date of John Houghton's execution. There are paintings of four of the Carthusian martyrs - Blessed William Exmew, Blessed Thomas Johnson, Blessed Richard Bere, and Blessed Thomas Green - at the Certosa di Bologna. Vincente Carducho was employed by the monks of the Chartreuse of el Paular to decorate the great cloister with 54 canvases of historical figures. Twenty-seven represent the life of St. Bruno, twenty-seven are
Portrait of a Carthusian the artist’s signature (the fly’s position right next to ‘Petrus ΧΡΙ Me Fecit’ hinting that the fly might be the referent of ‘me’ rather than the painting.) "Portrait of a Carthusian" featured a halo above the monk’s head when it was acquired by the Metropolitan Museum of Art in 1944. However, halos are extremely rare in Early Netherlandish painting and the one in "Portrait of a Carthusian" has long been an object of speculation. Finally in 1994, in preparation for the Met’s exhibition "Petrus Christus: Renaissance Master of Bruges", the authenticity of halo was publicly examined by a panel of