 In 1952, although Britten's collaboration with Crozier had ended, he used the Chester plays book as the source text for his "Canticle II", based on the story of Abraham and Isaac.In April 1957 Boris Ford, Head of Schools Broadcasting at Associated Rediffusion (A-R), wrote to Britten, proposing a series of half-hour programmes.These would show Britten composing and rehearsing a work through to its performance, and would provide children with "an intimate piece of musical education, by ... watching a piece of music take shape and in some degree growing with it".