Appointed in 1938, Sir John Rothenstein was the first director of the Tate to embrace modern art, mounting a series of daring exhibitions and procuring a procession of audacious masterworks that, in the words of one contemporary, 'completely knocked the stuffiness out of that veritable institution.' So why, since he died in 1991, has his name become a byword for reactionary conservatism? The answer is that from the outset of his career, Rothenstein refused to bow to the patriarchs of the avant-garde. In the 1920s, while they were busy decrying the figurative tradition, Rothenstein was...