Few fifteenth-century barons had more remarkable lives than Ralph, Lord Cromwell (d.1456). His long career has three distinct aspects. The first is that of the long-serving royal administrator, who devoted himself to the service of the house of Lancaster from the bright optimism of Henry V’s reign to the failure and alienation of the strife-torn 1450s. Then, beset by his enemies, he turned for protection to those who would later bring down the dynasty he had served so long. The second is that of a great builder, who, in his lifetime, created three great edifices – the castle at Tattershall with its striking brick donjon and the manorhouses at South Wingfield in Derbyshire and Collyweston in Northamptonshire, the last now lost – and who, in death, provided for the creation of a fourth, the massive collegiate church at Tattershall. Even in an age notable for the activity of its aristocratic builders, none of his contemporaries could match such a record of creation. The third aspect of his career is less admirable. Great buildings require great resources, and Cromwell was less than scrupulous in the means by which he augmented his wealth: he ruthlessly exploited the profits and influence attendant upon royal service to extend a baronial estate of fairly modest proportions into one of the greatest inheritances in England. In so doing he employed tactics in the acquisition of property that, according to contemporary complaints against him, went far beyond the generous prevailing norms of acceptable practice. All three of these themes came together in the execution of his will: the compromises he had made to win political support in his last years brought difficulties to his executors; his passion for building found a posthumous expression in the rebuilding of the churches at Tattershall and at his ancestral home of Lambley in Nottinghamshire; and his desire to make redress for past wrongs diminished the resources available to the executors and delayed the implementation of their ambitious charge.