June 1343. The College of Cardinals was now thoroughly French, with a strong accent of the Auvergne. On 19 May 1344 the two new cardinals who had died were replaced by two more Frenchmen: the Provençal Pierre Bertrand, the nephew of Cardinal Pierre Bertrand; and Nicolas de Besse, yet another papal nephew. Like his immediate predecessors, Clement was devoted to France, and he demonstrated his French sympathies by refusing a solemn invitation to return to Rome from the city's people, as well as from the poet Petrarch. To placate the Romans, however, Clement VI issued the bull Unigenitus Dei filius on 27 January 1343, reducing the interval between one Great Jubilee and the next from 100 years to 50 years. In the document he elaborated for the first time the power of the pope in the use of indulgences. This document would later be used by Cardinal Cajetan in the examination of Martin Luther and his 95 Theses in his trial at Augsburg in 1518. By then, Unigenitus was firmly fixed in Canon Law, having been added in the collection called Extravagantes. On 23 February 1343 Pope Clement appointed Pons Saturninus as his "Provisor of Works of the Palace", thereby beginning a program of construction and decoration that continued throughout his reign. It was immediately clear that the Pope had no intention of returning to Rome, and that he intended to provide offices and quarters for the various organs of the Roman Curia in the Palace. Pope Benedict XII, his predecessor, had built a palace, sufficiently accommodating for a Cistercian monk, but Pierre Roger had spent much of his career at the French Court and had imbibed its tastes for far greater display and ceremony. The Pope was, after all, a sovereign, and Clement intended to live and work in an appropriate state. He commissioned the new Tower of the Garde-Robe, the Audience (for the Auditors of the Rota), the new Papal Chapel and the grand staircase that led to it, and the Tour de la Gache (where the Audientia contradictarum, the appellate court for countersuits, had its offices). He was also responsible for the two new entrance façades. He also purchased the sovereignty of Avignon from Queen Joan I of Naples in 1348 for the sum of 80,000 crowns. The Black Death Clement VI was on the papal throne when the Black Death first struck Europe in 1347. This