Ever since its première just before the composer's death, Vaughan Williams's Ninth Symphony has divided critical opinion and remained something of an enigma. Yet the composer thought highly of the work, and went against his usual practice by preserving all the sketches. This study, the first of its kind on a work of Vaughan Williams, analyses the symphony and traces its genesis through hundreds of pages of sketches and drafts; it also offers a general introduction to the composer's working methods. The manuscripts show how the composer worked meticulously to create the complex expressive ambivalence of the finished work, transforming in the process simpler conceptions redolent of his earlier music. Most crucially, however, the sketches reveal an underlying programme, centred on the theme of innocent sacrifice and drawing on Hardy's Tess of the D'Urbervilles, Stonehenge, and Salisbury Cathedral. Vaughan Williams's new musical path in the symphony, it emerges, was closely allied to the continuing evolution of his visionary agnosticism.