Épernon, and Henry III of France, and between George Villiers, 1st Duke of Buckingham, and Charles I of England. In the first half of the 19th century, popular historians such as Charles Dickens and Charles Knight popularised Edward's life with the Victorian public, focusing on the king's relationship with his favourites and, increasingly, alluding to his possible homosexuality. From the 1870s onwards, however, open academic discussion of Edward's sexuality was circumscribed by changing English values. By the start of the 20th century, English schools were being advised by the government to avoid overt discussion of Edward's personal relationships in history lessons. Views on his sexuality have continued to develop over the years. By the end of the 19th century, more administrative records from the period had become available to historians such as William Stubbs, Thomas Tout, and J. C. Davies, who focused on the development of the English constitutional and governmental system during his reign. Although critical of what they regarded as Edward II's inadequacies as a king, they also emphasised the growth of the role of parliament and the reduction in personal royal authority under Edward, which they perceived as positive developments. During the 1970s the historiography of Edward's reign shifted away from this model, supported by the further publishing of records from the period in the last quarter of the 20th century. The work of Jeffrey Denton, Jeffrey Hamilton, John Maddicott, and Seymour Phillips re-focused attention on the role of the individual leaders in the conflicts. With the exceptions of Hilda Johnstone's work on Edward's early years and Natalie Fryde's study of Edward's final years, the focus of the major historical studies for several years was on the leading magnates rather than Edward himself, until substantial biographies of the king were published by Roy Haines and Seymour Phillips in 2003 and 2011. Cultural references Several plays have shaped Edward's contemporary image. Christopher Marlowe's play Edward II was first performed around 1592 and focuses on Edward's relationship with Piers Gaveston, reflecting 16th-century concerns about the relationships between monarchs and their favourites. Marlowe presents Edward's death as a murder, drawing parallels between the killing and martyrdom; although Marlowe does not describe the actual nature of Edward's murder in the script, it has usually been performed following the tradition that Edward was killed with a red-hot poker. The character of Edward in the play, who has been likened to Marlowe's contemporaries