The fifteenth-century chronicler, topographer, and antiquary, William Worcester, composed his political treatise, The Boke of Noblesse, first around 1451, and subsequently revised it twice, around 1475, when he intended to present it to Edward IV, along with a 'Codicil' of documents about past wars, to encourage and advise the king in his plans to invade France after England's disastrous defeats under Henry VI. William's autograph of this revision survives. The treatise was later presented by William's son to Richard III, with a new preface, also included in this edition. The treatise draws on diverse sources: older English and French history; classical or pseudo-classical works, including a section translated from Cicero; recent French authors, including Christine de Pizan; and the history of the French wars under Henry V and Henry VI, including eyewitness reports by Worcester's former employer Sir John Fastolf (1380-1459). It offers a record of military history and political thought in the fifteenth century and changing literary tastes on the cusp of the Renaissance. In addition to the treatise, many manuscripts survive with William's annotations, revealing his many debts to other sources. With the copious surviving records of his life, they give a unique insight into this medieval author's research and working methods.