Conservationists have started dismantling one of Canterbury Cathedral's biggest stained glass windows as part of a repairs programme.
Glass from the Great South Window is being removed so unsafe stone and metalwork fixtures can be repaired.
Some of the glass dates from the 12th Century and includes a series depicting Old Testament figures such as Methusaleh and Noah.
It is estimated the repairs will cost £500,000 and take up to 12 months.
Leonie Seiliger, the cathedral's head of stained glass, said: "It's arguably the most important stained glass in the country.
"We must make sure that the windows are safely stored to prevent any accidental damage during the repairs to the stonework."
It is thought that the metal bars holding the panes in place expanded and contracted with temperature changes, causing the stonework in the Great South Window to crumble.
The window and south entrance has been fenced off to protect the public from the risk of falling masonry.
Supporters of the 900-year-old cathedral are currently aiming to raise £50m for renovation works and recently received £460,000 for work on its library roof and windows.