Difficulties over the inheritance of the Plumpton's estates, of which much documentation survives as the Plumpton Correspondence, may have also been a factor in getting this licence to crenellate. His chosen heir, his son from his secret second marriage, did not get firm possession of Plompton until 1515.

Plumpton, Sir William (1404–1480), landowner and administrator. Like many young gentlemen of the day he saw service as a soldier in the war against France: in 1427–8, when he probably received his knighthood, and again, in 1435, as a captain in the retinue of John, duke of Bedford. From the late 1430s, however, his main interests centred on Yorkshire. In 1439 he became steward and master forester of the royal honour of Knaresborough and constable of Knaresborough Castle, and remained closely connected with the honour's administration for the rest of Henry VI's reign. Then, in 1442, the earl of Northumberland appointed him steward of his lordship of Spofforth and other estates in Yorkshire for life, with an annual fee of £10. To this was added in 1447, for his good service, a further £10. From November 1439, moreover, Plumpton's name appeared on the commission of the peace for the West Riding and he served as sheriff of Yorkshire (1447–8), and Nottinghamshire and Derbyshire (1452–3)... fought for the Lancastrians at Towton on 29 March 1461; his son and heir, another William, probably lost his life in the fighting; and since his patron, the third earl of Northumberland, perished there, it is hardly surprising that the next few years proved traumatic for him... Plumpton's appointment as steward of Spofforth was nevertheless renewed by Northumberland in 1472 and he managed to win a measure of royal favour as well: he served as justice of the peace in the West Riding for most of the 1470s, figured on several government commissions, and even received permission to fortify his manor house at Plumpton. (Dockray)