Duke of Norfolk, was interpreted as treason by Henry who reported it to the king. The two dukes agreed to undergo a duel of honour (called by Richard II) at Gosford Green near Caludon Castle, Mowbray's home in Coventry. Yet before the duel could take place, Richard decided to banish Henry from the kingdom (with the approval of Henry's father, John of Gaunt) to avoid further bloodshed. Mowbray was exiled for life. John of Gaunt died in February 1399. Without explanation, Richard cancelled the legal documents that would have allowed Henry to inherit Gaunt's land automatically. Instead, Henry would be required to ask for the lands from Richard. Accession After some hesitation, Henry met the exiled Thomas Arundel, former archbishop of Canterbury, who had lost his position because of his involvement with the Lords Appellant. Henry and Arundel returned to England while Richard was on a military campaign in Ireland. With Arundel as his advisor, Henry began a military campaign, confiscating land from those who opposed him and ordering his soldiers to destroy much of Cheshire. Henry initially announced that his intention was to reclaim his rights as Duke of Lancaster, though he quickly gained enough power and support to have himself declared King Henry IV, imprison King Richard (who died in prison under mysterious circumstances) and bypass Richard's 7-year-old heir-presumptive, Edmund de Mortimer, 5th Earl of March. Henry's coronation, on 13 October 1399 at Westminster Abbey, may have marked the first time since the Norman Conquest that the monarch made an address in English. Reign Henry procured an Act of Parliament to ordain that the Duchy of Lancaster would remain in the personal possession of the reigning monarch. The Barony of Halton was vested in that dukedom. Henry consulted with Parliament frequently, but was sometimes at odds with the members, especially over ecclesiastical matters. On Arundel's advice, Henry obtained from Parliament the enactment of De heretico comburendo in 1401, which prescribed the burning of heretics, an act done mainly to suppress the Lollard movement. In 1410, Parliament suggested confiscating church land. Henry refused to attack the Church that had helped him to power, and the House of Commons had to beg for the bill to be struck off the record. Henry's first major problem as monarch was what to do with the deposed Richard. After an early assassination plot was foiled in January 1400, Richard died in prison aged