Continuing in academia, he received a doctorate for his thesis on the French landscape artist Claude Joseph Vernet in 1971. From 1971 to 1986, he lectured at Leicester University. He then moved to America to act as Curator of French Art at the Museum of Fine Arts in Boston.
He rose to be Curator of the National Gallery of Art in Washington D.C.[1] In 1998, he organised one of the country's most successful exhibitions: Van Gogh's Van Goghs.[3]