The son of rich parents, Clark was introduced to the arts at an early age. Among his early influences were the writings of John Ruskin, which instilled in him the belief that everyone should have access to great art. After coming under the influence of the connoisseur and dealer Bernard Berenson, Clark was appointed director of the Ashmolean Museum in Oxford aged twenty-seven, and three years later he was put in charge of Britain's National Gallery. His twelve years there saw the gallery transformed to make it accessible and inviting to a wider public. During the Second World War, when the collection was moved from London for safe keeping, Clark made the building available for a series of daily concerts which proved a celebrated morale booster during the Blitz.