 Some minor works took place during the remainder of the 19th century and continued into the early 20th century . During the 1930s further maintenance work ensued that included a new roof to protect the vaulted ceiling of the south choir aisle . From 1960 onwards the crumbling sandstone blocks were replaced and new windows were fitted in the chapterhouse , which was re @-@ <unk> to preserve its vaulted ceiling . From 1988 to 2000 , the two western towers were substantially overhauled with a viewing platform provided at the top of the north tower . 
