[citation needed] Tensions with Scotland remained, to the extent that Poynings, his father, and other nobles were requested to stay and guard the border rather than attend Parliament, for which they were excused.

[10] In the late 1440s, the Yorkshire tenants of his father, the Earl of Northumberland, were in almost constant conflict with their neighbours, those of the Archbishop of York, involving armed skirmishes which Percy's brothers led.

A year later, Henry Percy – now Lord Poynings by right of his wife – took direct part, with his father, in raiding the manor of Newington Bertram in Kent, which was also enfeoffed by Robert.

[4] Although a reconciliation of the leading magnates of the realm was attempted in October 1458 in London, he arrived with such a large body of men (thought to be around 1,500)[21] that the city denied him entry.

[22] When conflict broke out again, he attended the so-called Parliament of Devils in October 1459, which condemned as traitors those Yorkists accused of, among other offences, causing the death of his father four years before.

[4][27] The estates of the Earls of Northumberland had traditionally been in constant use as a source of manpower and wages in defence of the border since the Percy family first gained the office the previous century.

[28] The wages assigned to the third Earl were substantial: £2,500 yearly in time of peace, and £5,000 during war, as well as an annual payment for the maintenance of Berwick's upkeep (£66 in peacetime and £120 in wartime).

[31] As a reward for his role in the Lancastrian victory at Ludford Bridge, he was made Chief Forester north of the River Trent and the Constable of Scarborough Castle on 22 December 1459 for life.

This charge was likely to have had some truth in it, as it was his continued pillaging of those estates, with the Lords Clifford and Dacre, that led to York marching north to Wakefield in December 1460.

These incomes, however collected, would have been vital to the Earl both personally and militarily as his northern estates especially had been a victim of feudal decline for most of the first half of the fifteenth century: even on the forfeit of the earldom to the Crown in 1461, his arrears have been calculated as still standing at approximately £12,000.