On 24 June 1908 John Bilson, a minor architect from Hull, visited Bayeux. After lunch at the Hôtel du Luxembourg, reported as ‘good, 3 fr’, he went to the cathedral. As was his wont, he recorded his visit with detailed notes and sketches. But instead of glorying in the Gothic beauties of the choir, or puzzling over the chronology of the nave, he focused his attention on the crypt and, in particular, on the ground floor chamber in the north-west tower (Figure 1). His peculiar interest is confirmed by a return visit two years later, again carefully recorded in his pocketbook. Preoccupation with this area might initially seem strange: compared with the other parts of the cathedral its architecture is unadorned, it has no obvious ritual significance other than as a secondary entrance, and any archaeology in the form of masonry breaks was hidden under plaster. What attracted him to the spot were the arches, traversing the space from springing points in the centre of each wall. As this paper aims to explain, interest in early vaulting techniques, particularly those involving arches, was dependent on more than the personal idiosyncrasies of a provincial architect and still has much to tell us about how we understand eleventh- and twelfth-century buildings. Study of John Bilson is thus not merely an exercise in biographical historiography (and for reasons of space, biographical information is largely excluded from the present article). Instead, it provides the opportunity to explore what might be termed a paradigm shift in architectural history, demonstrating how one man’s work forced a generation of scholars to reconsider their fundamental principles.

Bilson made significant contributions to many architectural debates but the most important was undoubtedly his research on Durham Cathedral (Figure 2). Durham is universally recognized as a masterpiece of English Romanesque – a style sometimes called Norman – identified as such by its round arches and its massive piers, which alternate between drum and compound forms, both typical of the style. Yet coeval with these features, Durham also has pointed arches, ribbed vaults, and roof supports in the form of proto-flying buttresses (not fully fledged because they remain hidden beneath the aisle roofs). Of course, Durham Cathedral is not a Gothic building – a fact which seems so obvious that it hardly needs stating.