The slide from December 1318 onwards into the civil war of May 1321 must have been a terrifying experience for those who lived through it, especially as the Scots were ravaging the northern border. The younger Despenser was creating a frighteningly novel situation. He was seizing any neighbour's lands that he desired and covering himself with royal grants to achieve virtual immunity. The violence and desperation of his opponents is easy to understand. His new Welsh tenants were also restive and the rapidity with which his lands were to fall to his enemies in 1321 reveals the reluctance of his new vassals to fight for him and his Clare wife.

By 1319 two situations had arisen which decisively drove the Marchers into opposition to Despenser. One was border skirmishing between John Giffard of Brimpsfield's tenants of Cantref Bychan and Despenser's men in Cantref Mawr. On the Marcher side there was clearly anxiety that Despenser intended to expand in this direction. Despenser was probably nervous because of his suspicions of his Welsh tenantry there. John Giffard of Brimpsfield was an important man, the owner of relatively few manors but very rich ones and he himself was known as John the Rich. He was also very well connected and came from a family with many branches, one of which had recently produced an archbishop of York and a bishop of Worcester.