In late November 1384, the politicians and public gathered at Westminster for a session of parliament were treated to a spectacle in the form of a trial by combat between the English esquire John Walsh and Martel de Villeneuve, an esquire from Navarre. The combat took place under the judicial auspices of the Court of Chivalry, a court headed by the Constable and Marshal of England with authority devolving directly from the king. This court operated according to the law of arms, which used civil law procedures, and its remit included dealing with military disputes that originated outside the realm as well as knightly and noble conflicts over heraldic arms and other matters of honour. It was one of the judicial venues that could be used to try treason and it was an accusation of treason that brought the two combatants into the lists at Westminster on that late November day. Martel had accused Walsh – the king's receiver at the English castle of Cherbourg – of planning to sell out the castle to the French. The St Albans Chronicle added that Walsh had sexually assaulted Martel's wife, asserting that it was this insult that lay at the root of Martel's treason accusation. Things did not end well for the accuser: Walsh emerged the victor so Martel was immediately stripped of his armour, drawn from Westminster Palace through the London streets and out to the public gallows at Tyburn, where he was hanged and beheaded.

Neither of the combatants play any further part in this narrative but the 1384 incident does bring to light several themes relevant to struggles over treason that began in 1386 and culminated in the trials and executions of 1388's Merciless Parliament. The first was the fluid meaning of treason, with the chronicle accounts reflecting legal and military definitions of treason but also the cultural sense of treason as a betrayal of masculine bonds. Second was the question of how treason should be tried and by whom. This question had been left unanswered in the 1352 statute, which stated simply that uncertain cases should be brought before the king in parliament. In theory, the Court of Chivalry was limited to judging disputes arising outside the realm but in practice, its existence as a potential trial venue influenced strategy and tactics on both sides of the 1386–8 conflict.