During the final years of his extraordinarily productive life - spent in Rome in the service of Giuliano de’ Medici and in France at the court of King Francis I - Leonardo accomplished some of his greatest feats in the realms of art, engineering and architecture, while pioneering almost single-handedly the study of human anatomy. It was in this period that he at last succeeded in bringing to completion such renowned artworks as the Mona Lisa, the Saint Anne and the Leda. Furthermore, with the help of his talented young assistant, Francesco Melzi, he endeavoured to compile his vast trove of observations and scientific inquiries into treatises fit for publication. In contrast to his earlier practice, he now strove to complete what he had previously left in abeyance. In order to tell the full story of Leonardo’s final years, the author has conducted a thorough reassessment of the available evidence in the light of contemporary historical events, while drawing on hitherto unknown primary sources, identified in the course of a decade of systematic archival research. As a result, it has become possible to fill numerous gaps in current knowledge, while sweeping away misconceptions and previously unchallenged assumptions. What emerges is a fresh and more authentic picture of this critical period of Leonardo’s life.