presence of the crucified Christ. It is behind the curtains in the upper left hand corner. This raises the portrait to a higher level, as does the skull: despite their status and intellectual activities these men remain sinful and mortal human beings,and answerable to God. There are many other messages in the painting - the floor mosaic on which the skull lies, is based on a design in Westminster Abbey, the Cosmati pavement, which is situated before the High Altar, and the carpet on the upper shelf is notably oriental. Such carpets were often integrated into Christian imagery as symbols of luxury and status. The painting has caused much controversy over the years. One Science Historian, Professor John North, analysed the scientific and mathematical elements shown in the painting. He calculated the time given in the portrait as 4 pm on Good Friday, 11th April 1533, 1500 years exactly after the Crucifixion, with the key to the painting to be found in the small crucifix. Sunday, 24 February 13