The 12th- and 13th-century early Gothic churches from the region around Paris which form the basis of this study were large-scale undertakings. Dr James draws on evidence which suggests that work proceeded in a series of projects, when funding, technical problems (for example, slow-setting mortar), and the work of other trades (such as roofing and centring) allowed. Within each project there were generally a number of separately organised phases, or 'campaigns', and it is from close study of these campaigns that the author proceeds to an identification of the characteristics of the individual master masons, the template-makers.