Henry II granted to the citizens of Exeter the first of their many charters of privileges, and in the reigns of King John and Henry III the municipal system was very much developed, and the city first had a Mayor. Under Edward I a beginning was made towards the almost entire reconstruction of the Cathedral. Bishop Warelwast, the nephew of William I, had raised the transeptal towers--a feature that no other English cathedral possesses--and since his time the Lady Chapel had been added, but the design of the Cathedral as a whole was evolved by Bishop Quivil. He planned what was practically a new church, and his intentions were faithfully carried out. Before his day the towers were merely 'external castles,' but Bishop Quivil broke down their inner walls, and filled the space with lofty arches, and the towers became transepts. Bishop Stapledon spent huge sums in collecting materials, but before much progress with the work had been made he was murdered by a London mob, in the troubled reign of Edward II; and the actual existence of much of the building is due to Bishop Grandisson, who, sparing himself in no matter, lavished treasure and devotion on his Cathedral. Writing to Pope John XXII, the Bishop said 'that if the church should be worthily completed, it would be admired for its beauty above every other of its kind within the realms of England or France.' One of the most beautiful features of the Cathedral is the unbroken length of roof at the same height through nave and choir, the effect intensified by the exquisite richness and grace of the vaulting. And the spreading fans gain an added grace, springing as they do from that 'distinctive group of shafts' which, says Canon Edmonds, 'makes the Exeter pillar the very type of the union of beauty and strength.' In the central bay of the nave, on the north side, is the Minstrels' Gallery, one of the few to be found in England. It is delicately and elaborately sculptured, and each of the twelve angels in the niches holds a musical instrument--a flageolet, a trumpet and two wind instruments, a tambour, a violin, an organ, a harp, bagpipes, the cymbals, and guitars.