Hampden's mortal wounding at Chalgrove and death in June 1643 remains a matter of controversy through reliance of existing accounts on tainted evidence, extending from the supposed account of Edward Hyde, Lord Clarendon in the seventeenth century through politically motivated partisan interpretation in the eighteenth century to the largely falsified account of George, Lord Nugent in the nineteenth century. The author's research in the Bodleian Library, Oxford discovered Clarendon's contemporary account, which revealed that the accepted version of the Battle of Chalgrove published in the celebrated posthumous edition of his History of the Rebellion in 1702 bore little relation to the original text. The fictions and propaganda incorporated in the published text by Clarendon's son, Lawrence Hyde, continued to mislead historians. Hampden's memory was exploited for partisan purposes by several authors in the eighteenth century, with new fictions and falsified evidence perpetrated in the nineteenth century by Hampden's equally partisan biographer, Lord Nugent, and writers such as Eliot Warburton. These accounts have been accepted by modern authors including the latest last biographer of Hampden (1976), and continue to mislead The Battlefields Trust and Historic England in their interpretations of Chalgrove. All these fictions and the motivations underlying them are examined in detail including those related to Hampden's supposed funeral and exhumation by Lord Nugent of what he claimed to be Hampden's body. In presenting a new account of Chalgrove based on wide research including estate maps and exceptional knowledge of the terrain, the author not only challenges the accepted version of Chalgrove and its consequences but points to the need for a reevaluation of what is perceived to be Clarendon's history of the Civil Wars. Hampden's wider legacy, not least in North America, is also examined in a major contribution to the contribution to the historiography of the First Civil War. Ironically, Voltaire proclaimed, "All gazettes of Battles are Liars, the English perhaps, the least of any." The example of Chalgrove suggests he was mistaken. There are nine chapters which establish Hampden's significance, the cause and course of the battle, its military and political consequences, and the subsequent historiography. In addition, appendices reproduce the key primary texts. AUTHOR: The author's understanding of the English Civil War was learned leading re-enactors of John Hampden's 'Greencoat' Regiment onto famous English Civil War battlefields. He successfully challenged English Heritage to have the encounter at Chalgrove on its Register as a Battle. He wrote The Controversy of John Hampden's Death (2000), which exposed the facts about John Hampden's supposed exhumation. Oxoniensia published the author's research (2015), which was subsequently accepted by the Victoria County History. The author discovered Clarendon's private journal, which revealed the celebrated The History of the Rebellion (1702) to be fiction. The Journal of the Society for Army Historical Research published his article 'Clarendon and History' in 2021. 25 colour & b/w ills, maps