from the cathedral; there was much destruction of tombs, windows and altars. In the English Civil War the city was besieged and fell to the forces of Cromwell in 1644, but Thomas Fairfax prevented any further damage to the cathedral. Following the easing of religious tensions some work was done to restore the cathedral. From 1730 to 1736 the whole floor of the minster was relaid in patterned marble and from 1802 there was a major restoration. However, on 2 February 1829, an arson attack by Jonathan Martin inflicted heavy damage on the east arm. An accidental fire in 1840 left the nave, south west tower and south aisle roofless and blackened shells. The cathedral slumped deeply into debt and in the 1850s services were suspended. From 1858 Augustus Duncombe worked successfully to revive the cathedral. In 1866, there were six residentiary canonries: of which one was the Chancellor's, one the Sub-Dean's, and another annexed to the Archdeaconry of York. During the 20th century there was more concerted preservation work, especially following a 1967 survey that revealed the building, in particular the central tower, was close to collapse. £2,000,000 was raised and spent by 1972 to reinforce and strengthen the building foundations and roof. During the excavations that were carried out, remains of the north corner of the Roman Principia (headquarters of the Roman fort of Eboracum) were found under the south transept. This area, as well as remains of the Norman cathedral, re-opened to the public in spring 2013 as part of the new exhibition exploring the history of the building of York Minster. 1984 fire On 9 July 1984, York Minster suffered a serious fire in its south transept during the early morning hours. Firefighters made a decision to deliberately collapse the roof of the south transept by pouring tens of thousands of gallons of water onto it, in order to save the rest of the building from destruction. A total of 114 firefighters from across North Yorkshire responded to the fire and contained it, while York Minster's staff and clergy rushed to preserve historical objects in the building. The glass of the south transept rose window was shattered by the heat but the lead held it together, allowing it to be taken down for restoration. A subsequent investigation found an 80% chance that the fire was caused by a lightning strike to a metal electrical box atop