At a young age, he was made Warden of the Marches towards Scotland in 1362, with the authority to negotiate with the Scottish government.

Percy and Hotspur were given the task of subduing the rebellion of Owain Glyndŵr, but their attempts to make peace with the Welsh rebels did not meet with the king's approval.

In September 1402 the Percys took part in the Battle of Homildon Hill, which led to the capture of many Scots nobles.

In 1408 Percy invaded England in rebellion once more and was killed at the Battle of Bramham Moor.

[5] They had four sons (Harry "Hotspur" Percy, Thomas, Ralph, and Alan) and one daughter (Margaret).

His position as a character in the Shakespearean canon inspired the character of Lord Percy Percy, heir to the duchy of Northumberland in the historical sitcom The Black Adder, set during the very late Plantagenet era.