Its deterioration was arrested in the 19th century , by which time the building was in a substantially ruinous condition .
After the removal of the lead that waterproofed the roof in 1567 , the cathedral steadily fell into decay .
cathedral 's deterioration was arrested in the 19th century , by which time the building was in a substantially ruinous condition .
After the removal of the lead that waterproofed the roof in 1567 , the cathedral steadily fell into decay .