On 25 September 1403, an urgent and quite revealing meeting of the king's council took place within the precincts of Durham Priory. Chaired by Ralph Neville of Raby, earl of Westmorland and the king's brother-in-law, the meeting was partly a post mortem on the failed Percy rebellion, culminating in the battle of Shrewsbury, and partly a planning session. Westmorland himself had become, over the previous half-decade, a figure of great national importance; already possessed of a talent for service and sharp political acumen, his marriage to John of Gaunt's daughter, Joan Beaufort, had brought him into the royal family and its inner circle, making him a formidable figure indeed. Present also were other important Lancastrians, among them Earl Ralph's brother Thomas, Lord Furnival; the bishop of Durham's palatine steward, Sir Ralph Eure; the Northumberland sheriff, Sir John Mitford; and Westmorland's own son-in-law Peter, Lord Mauley, recently wed to Maud Neville, the earl's daughter from his first marriage to Margaret Stafford. Called in the wake of the king's victory the prior July over the Percys and their fellow conspirators at Shrewsbury, the group took as its most immediate concern the surrender of the Percy castles in Northumberland, and the effective decommissioning of the senior Henry Percy's power base in the region, which had been constructed over the preceding three decades and more.

Modern scholars, taking their cues in part from contemporary chroniclers, have portrayed the Percys as near-mythical figures in the far north, ascribing to them the singular ability to earn and maintain the fierce loyalty of the region's shire knights. In the event, this process of decommissioning in Northumberland would take nearly three further years to achieve, as Percy retainers, ensconced as captains of strategic fortresses across the Scottish frontier, consistently stood firm against the king's men – indeed, remarkably so. Only with the appearance of a rather large royal artillery train in 1406 did their resolve meet a severe test, and cause them to yield. Yet if the near-term goals of the 1403 Durham council were not immediately met, its larger import has nonetheless been overlooked. Not only did those present at Durham that day ultimately achieve for Henry IV what his predecessor had never enjoyed – lasting and reliable control over the far northern reaches of his realm – the council meeting itself was also emblematic of the shift toward the new king's employment of his own, private retainers in the management of his kingdom.