It's never good when a famous painting gets damaged! There are different types of damage that can affect paintings, some of them accidental, some intentional – such as the vandalism which affected The Rokeby Venus in 1914.
A lot of the work done here at National Gallery is actually repairing the damage to paintings. There is a painting that was very difficult for the gallery to fix!

Rhubarb (Fruit & Root Crew)
05:45

Hear Susanna's Safety Seymour radio ad!
01:52

Carrots (Fruit & Root Crew)
05:13