In this work, which has survived only in manuscript form and in Italian, Gardiner analyses the great dynastic changes in England's past in order to provide Phillip II with a guide to ruling England and establishing a Catholic dynasty. He adapts historical example to practical political purposes with great subtlety, quoting at length (but without saying so) from Machiavelli to show that a new prince can rule England - if he eliminates those of royal blood and respects the laws and customs of his new possessions. This edition is a carefully edited text of the Italian and Professor Donaldson has provided an English translation and an introduction setting the treatise in its immediate historical context. Gardiner's work is perhaps the clearest example of an attempt to relate Machiavelli's political theories to practical political problems. Its publication will interest historians and students of politics as well as those with an interest in the influence of Machiavellianism as an important strand in European intellectual history.