The eighteen years that Leonardo da Vinci spent at the court of Ludovico il Moro had such an impact on the history of Lombard art that the whole 16^th century was affected. Leonardo started work on the fresco - judged by many the genius's greatest work - in 1496 when he received a commission from Ludovico who, after having enlarged the church of Santa Maria delle Grazie, decided to enlarge and decorate the Refectory (Dining Hall) of the adjacent Dominican monastery. Leonardo's snail pace work on the fresco soon became legendary. In fact, in a letter sent by Ludovico to Marchesino Stampa dated June 29, 1497, Ludovico specifies that "we have made the heartfelt decision... to urge Leonardo the Florentine to finish the work he has undertaken in the Refectory of Santa Maria delle Grazie". Leonardo painted it using an unconventional technique, sometimes without letting of a paintbrush the whole day long, other times not picking up a paintbrush for days at a time. Unfortunately, this technique involving the use of tempera paint over a double layer of plaster (rather then true fresco pigment which becomes part of the wall itself) proved faulty, and the fresco, which could not withstand the dampness of the wall it was painted on, was soon decaying. By 1568, the writer-artist Vasari could already write of a "striking stain". This was due to moisture collecting under the paint, causing the pigment layer to fall off, the formation of saltpetre and the spreading of mould. The tempering of French mercenary troops in the 16^th century followed by Napoleon's soldiers in the 18^th century worsened these inherent defects. Emerging miraculously unscathed from the August 1943 bombings which meanwhile had completely destroyed the Refectory, the Last Supper was given the best of modern restoration treatment to save it from total ruin (numerous past attempts had miserably failed). Leonardo put great emphasis on the depth out of which the twilight emanates to bathe the figures in its uniform glow. The whole scene is bathed in a diffuse, gentle light coming partly from three windows at the far end of the room and partly from the light at the front, which seems to come from the actual window in the real room. The apostles are placed in a group of three along the horizontal plane of the table whose centre is the fixed point of the Christ figure. All the lines of the rigorously symmetrical composition converge on Him in perfect perspective, including the gestures and glances of the apostles, each of whom is portrayed reacting differently according to his psychological state, to the words of Christ: "One of you would betray me".