What Must Happen has concerns which might be grouped under three headings. First there are personal, mainly elegiac poems that recall parents, relations and friends. The second grouping, including the title poem, has poems on wider historical subjects some of which relate to the personal through Wainwright's recollections of his upbringing and the history of the Potteries. This group also includes a series of contemporary characterisations of some of the Roman gods. Thirdly the collection includes some extensive sequences best described as 'variations' in that they reiterate and vary particular words, phrases, images and most importantly rhythms.