 Simon de Montfort had seized power in England following his victory over Henry III at the Battle of Lewes during the Second Barons ' War , but his grip on the country was under threat . In an attempt to gather more support he summoned representatives from not only the barons and the knights of the <unk> , as had occurred in previous parliaments , but also burgesses from the major towns . The resulting parliament in London discussed radical reforms and temporarily <unk> Montfort 's political situation . Montfort was killed at the Battle of Evesham later that year , but the idea of inviting both knights and burgesses to parliaments became more popular under the reign of Henry 's son Edward I. By the 14th century this had become the norm , with the gathering becoming known as the House of Commons . This parliament is sometimes referred to as the first English parliament and Montfort himself is often termed the founder of the Commons . 
