of stone, 3,000 tons of timber and 450 tons of lead were used in the construction of the cathedral. Although the spire is the cathedral's most impressive feature, it has proved troublesome. Together with the tower, it added 6,397 tons (6,500 tonnes) to the weight of the building. Without the addition of buttresses, bracing arches and anchor irons over the succeeding centuries, it would have suffered the fate of spires on other great ecclesiastical buildings (such as Malmesbury Abbey, 1180 to 1500; Lincoln Cathedral, 1311 to 1548; Old St Paul's Cathedral, London, 1314 to 1561; and Chichester Cathedral, 1402 to 1861) and fallen down; instead, Salisbury became the tallest church spire in the country on the collapse at St Paul's (as the result of a fire) in 1561. The large supporting pillars at the corners of the spire are seen to bend inwards under the stress. The addition of reinforcing tie-beams above the crossing, designed by Christopher Wren in 1668, halted further deformation. The beams were hidden by a false ceiling installed below the lantern stage of the tower. Significant changes to the cathedral were made by the architect James Wyatt in 1790, including the replacement of the original rood screen and demolition of a bell tower which stood about northwest of the main building. Salisbury is one of only three English cathedrals to lack a ring of bells, the others being Norwich Cathedral and Ely Cathedral. However, its medieval clock does strike the time with bells every 15 minutes. 21st century In February 2016, the cathedral chapter placed Sophie Ryder's sculpture The Kiss straddling a path on the grounds where it was to remain until July. After only a few days, the work had to be moved, as pedestrians kept bumping into it while texting. On 25 October 2018, there was an attempted theft of the cathedral's copy of Magna Carta; the alarms were triggered and a 45-year-old man was later detained on suspicion of attempted theft, criminal damage and possession of an offensive weapon. The outer layer of a double-layered glass case containing the document was broken, but the document suffered no damage. In January 2020 the perpetrator, Mark Royden, aged 47, from Kent, was found guilty of the attempted theft, which caused £14,466 of damage, and guilty of criminal damage. From 16 January 2021, while closed to services during the COVID-19 pandemic, the cathedral was used to