They would have been large fellows. Estimates differ, but the draw weight of an English war bow seems to have been somewhere between 90 and 140 foot-pounds (draw weight means the amount of force in the bow when its string is pulled to the max). Further explanation would get rather technical, but rest assured: The bow packed a wallop, and an arrow tipped with a bodkin point could easily penetrate mail armor. There are also historical accounts of bodkin-tipped arrows penetrating steel armor at close range.
from Frank Wilson: The Philadelphia Inquirer: Grand climax stars English bow