Shortly before the outbreak of World War II the paintings were evacuated to locations in Wales, including Penrhyn Castle, the university colleges of Bangor and Aberystwyth. In 1940, during the Battle of France, a more secure home was sought, and there were discussions about moving the paintings to Canada. This idea was firmly rejected by Winston Churchill, who wrote in a telegram to the director Kenneth Clark, "bury them in caves or in cellars, but not a picture shall leave these islands". Instead a slate quarry at Manod, near Blaenau Ffestiniog in North Wales, was requisitioned for the Gallery's use. In the seclusion afforded by the paintings' new location, the Keeper (and future director) Martin Davies began to compile scholarly catalogues on the collection, with assistance of the Gallery's library which was also stored in the quarry. The move to Manod confirmed the importance of storing paintings at a constant temperature and humidity, something the Gallery's conservators had long suspected but had hitherto been unable to prove. This eventually resulted in the first air-conditioned gallery opening in 1949.
