In 1601, as the reign of Elizabeth I drew to a close, the civil lawyer Thomas Wilson identified the prevailing uncertainty over the English succession: 'upon whose head it will fall is by many doubted'. During the first decade of the last Tudor monarch's reign, however, Lady Katherine Grey, great-granddaughter of the first Tudor king, Henry VII, and sister of the ill-fated Lady Jane, was widely viewed as the heir to Elizabeth's throne, especially by Protestants hostile to the prospect of a Catholic succession. This book proposes a re-examination of the life and legacy of Katherine Grey in the context of late sixteenth-century succession debates, sexual intrigue and Reformation politics. Katherine's importance as a claimant to the throne of Elizabeth I will also be explored with regard to contemporary attitudes to female monarchy. While Katherine has usually been identified as a tragic figure, her significance as heiress to the crown, according to the last will and testament of Henry VIII, has perhaps been neglected given that Elizabeth was eventually succeeded by James VI of Scotland, son of the executed Mary, Queen of Scots. If the wishes of Henry had been followed, however, then it would surely have been Katherine's eldest son, Edward, who became king of England in the spring of 1603. AUTHOR: Conor Byrne is the acclaimed author of Katherine Howard: Henry VIII's Slandered Queen (THP, 2018). He was a regular contributor to Tudor Life Magazine and has run a popular historical blog since 2012. 16 colour illustrations