it was not a cathedral, because the seat of the diocese was at Dorchester Abbey in Dorchester-on-Thames, Oxfordshire). However, Lincoln was more central to a diocese that stretched from the Thames to the Humber. Remigius built the first Lincoln Cathedral on the present site, finishing it in 1092 and then dying on 7 May of that year, two days before it was consecrated. In 1124, the timber roofing was destroyed in a fire. Alexander (bishop, 1123–48) rebuilt and expanded the cathedral, but it was mostly destroyed by an earthquake about forty years later, in 1185 (dated by the British Geological Survey as occurring 15 April 1185). The earthquake was one of the largest felt in the UK: it has an estimated magnitude of over 5. The damage to the cathedral is thought to have been very extensive: the cathedral is described as having "split from top to bottom"; in the current building, only the lower part of the west end and its two attached towers remain of the pre-earthquake cathedral. Some (Kidson, 1986; Woo, 1991) have suggested that the damage to Lincoln Cathedral was probably exacerbated by poor construction or design, with the actual collapse most probably caused by a vault failure. After the earthquake, a new bishop was appointed. He was Hugh de Burgundy of Avalon, France, who became known as St Hugh of Lincoln. He began a massive rebuilding and expansion programme. With his appointment of William de Montibus as master of the cathedral school and chancellor, Lincoln briefly became one of the leading educational centres in England, producing writers such as Samuel Presbiter and Richard of Wetheringsett, though it declined in importance after William's death in 1213. Rebuilding began with the choir (St Hugh's Choir) and the eastern transepts between 1192 and 1210. The central nave was then built in the Early English Gothic architectural style. Lincoln Cathedral soon followed other architectural advances of the time – pointed arches, flying buttresses and ribbed vaulting were added to the cathedral. This allowed support for incorporating larger windows. There are thirteen bells in the south-west tower, two in the north-west tower, and five in the central tower (including Great Tom). Accompanying the cathedral's large bell, Great Tom of Lincoln, is a quarter-hour striking clock which was installed in the early 19th century. The two large stained glass rose windows, the matching Dean's Eye and the Bishop's Eye were added