A skaldic tradition describes the bridge's destruction in 1014 by Æthelred's ally Olaf, to divide the Danish forces who held both the walled City of London and Southwark. The earliest contemporary written reference to a Saxon bridge is c.1016 when chroniclers mention how Cnut's ships bypassed the crossing, during his war to regain the throne from Edmund Ironside (see Battle of Brentford (1016)). Following the Norman conquest in 1066, King William I rebuilt the bridge. The London tornado of 1091 destroyed it, also damaging St Mary-le-Bow. It was repaired or replaced by King William II, destroyed by fire in 1136, and rebuilt in the reign of Stephen. Henry II created a monastic guild, the "Brethren of the Bridge", to oversee all work on London Bridge. In 1163, Peter of Colechurch, chaplain and warden of the bridge and its brethren, supervised the bridge's last rebuilding in timber. After the murder of his erstwhile friend and later opponent Thomas Becket, Archbishop of Canterbury, the penitent King Henry II commissioned a new stone bridge in place of the old, with a chapel at its centre dedicated to Becket as martyr. The archbishop had been a native Londoner and a popular figure. The Chapel of St Thomas on the Bridge became the official start of pilgrimage to his Canterbury shrine; it was grander than some town parish churches, and had an additional river-level entrance for fishermen and ferrymen. Building work began in 1176, supervised by Peter of Colechurch. The costs would have been enormous; Henry's attempt to meet them with taxes on wool and sheepskins probably gave rise to a later legend that London Bridge was built on wool packs. After Colechurch's death, Isembert, a French monk who was renowned as a bridge builder, was appointed by King John to complete the project. Construction was not finished until 1209 during the reign of King John. John tried to recoup the cost of building and maintenance by licensing out building plots on the bridge but this was never enough. In 1284, in exchange for loans to Edward I, the City of London acquired the charter for the maintenance of the bridge, based on the duties and toll-rights of the former "Brethren of the Bridge". The bridge was wide according to some records that were later disputed. The structure was about long, supported by 19 irregularly spaced arches, founded on starlings set into the river-bed.