The Manod slate quarry near Blaenau Ffestiniog was used to keep masterpieces safe during World War II, efforts to protect priceless artworks from harm were made as soon as war was declared in 1939.

Manod proved so successful that, in the 1950s, long after the National Gallery’s paintings were back on the walls in London, it was the planned destination for Britain’s art treasures in the event of a third world war.