Architectural practice is the study of how people produce architecture - the ways in which they build, the manner in which they organize themselves to do so and the methods by which buildings are both conceived and physically realised. This thesis is concerned with investigating what has been seen as the watershed period between medi~v.al and modem practices. It particularly examines whether the picture of late 17th century development given by John Summerson in 'Georgian London' (1945), still the standard work on the subject, is correct. In order to do this new evidence has been used from the Court of Chancery concerning building and property disputes. The first section 'Development Practice' investigates where and how development was carried out. It shows how the development system was made possible through the freehold/leasehold distinction in English law which allowed for separate interests to exist in the same piece of land. It proves that it was undertaken not primarily by aristocrats, as Summerson thought, but by a new breed of businessmen and entrepreneurs working largely on credit. The next section 'Design Practice' examines the design process for the realisation of these projects. It shows that although the antecedents of the new houses being produced were classical this was not matched by a parallel transformation in design procedures or the understanding of form. Only a very limited use was made of drawings and where they were used, it is argued, this was mainly for contractual or economic purposes. This section challenges conventional notions about the adoption of classicism in this country and its use and tranmission here. In the final section 'Building Practice' the role of the craftsman is examined and is shown to be far more entrepreneurial than conventional interpretations have allowed, with some of them operating as master builders contracting for all trades. It is shown that the new classical house with its regular, standardized parts was perfectly suited to the design, construction and development systems of the day, and that building was a far more capitalistic and commercialized activity by this date than has previously been thought.