See https://en.wikipedia.org/wiki/Humphrey_de_Bohun,_4th_Earl_of_Hereford
Humphrey (VI) de Bohun, 4th Earl of Hereford (1276 – 16 March 1322) was a member of a powerful Anglo-Norman family of the Welsh Marches and was one of the Ordainers who opposed Edward II's excesses.
Under King Edward I, Humphrey took part in many campaigns against the Scots.
He was later appointed Constable of England.
At the Battle of Bannockburn he should have led the English attack, but was out of favour with King Edward II. Instead the inexperienced Gilbert de Clare, Earl of Gloucester,led the attack with disastrous results for the English. However Humphrey fought bravely throughout the battle.
His young nephew Henry de Bohun single-handedly attacked Robert The Bruce during the battle but was famously killed by a single blow from Bruce's battle axe.
Humphrey like his father, grandfather and great-great grandfather had joined with other barons to insist that the king of ther day obey Magna Carta.
He was killed at the Battle of Boroughbridge in Yorkshire in 1322, supporting King Edward II against some rebellious barons.