Brindisi. When William soundly defeated the rebels, Adrian—who was by now, even more, bogged down in the problem of Rome and without allies—had to sue for peace on the King's terms. This was yet another external event—indeed, probably the single most important event of the pontificate she argues—that Adrian had had no way of influencing but had to deal with its consequences, notes Duggan. He was effectively captured and forced to come to terms at Benevento three weeks later. This one event, says Duggan, changed Adrian's policy for good, whether or not he liked it. As a result, at the Concordat of Benevento, Adrian had to invest William with the lands he claimed in southern Italy, symbolised by the presentation of the Pope's own pennoned lances and the kiss of peace. The Pope was accepted as William's feudal overlord, while being forbidden from entering Sicily without an invitation from the King, thereby granting William effectively Legatine authority over the church in his own land. For his part, William gave the Pope his homage and contracted to pay an annual tribute and provide military support on request. The treaty conferred extended powers on the Kings of Sicily that they would enjoy for at least the next 40 years, and included powers over ecclesiastical appointments traditionally held by the Popes as the region's feudal lord. Adrian's treaty with William angered the Emperor, who took it as a personal slight that Adrian had treated with the two Imperial rivals to Italy and confirmed his view of Adrian's Papal arrogance. This, suggests Robinson, sowed the seeds of the disputed election following Adrian's death. The defeat of Manuel's army left the Pope vulnerable, and in June 1156 Adrian was forced to come to terms with the Sicilian King. This was, however, suggests Robinson, on generous terms, including "homage and fealty, reparation for the recent encroachments on the papal patrimony, help against the Romans, freedom from royal control for the Sicilian church". Adrian's new alliance with William exacerbated relations with Barbarossa, who believed that Adrian had broken the Treaty of Constance twice over, by allying with both King William and the Byzantine Emperor. Relations between Pope and Emperor were, argues Latowsky, "irreparably damaged. Adrian probably acted as mediator the following year in concluding a peace treaty between William and Manuel. The Emperor attempted to prevent the treaty by sending his most experienced diplomat, Abbot Wibald to