This essay examines how England’s medieval parliamentary history – from Henry III to Henry IV – was deployed for polemical purposes in the months surrounding the outbreak of the Civil Wars. In particular, the aim is to both acknowledge and move beyond the ‘baronial context’ of the English Civil Wars, in which reflections on medieval history were used to justify a form of ‘parliamentarian’ rhetoric that afforded the peerage a decisive role. By examining a range of neglected popular pamphlets that appeared in print during the months leading up to conflict, the essay demonstrates instead how evidence relating to the fourteenth century began to be used to reflect on parliamentary power and on the House of Commons, and to discuss the possibility of deposing and executing ‘unprofitable’ kings and of electing and binding their successors. Attention is drawn to an important shift in parliamentarian rhetoric regarding the king and parliament. It is argued that the treatment of medieval parliaments reveals incipient political radicalism in the opening weeks and months of the Civil Wars.