Complex sentence: Sir Peter de Montfort (c.1215--4 August 1265) is said to have presided over a meeting of the Parliament of England at a Parliament held in Oxford in 1258.
Split into simpler sentences: Sir Peter de Montfort (c.1215--4 August 1265) was an English parliamentarian. He is said to have presided over a meeting of the Parliament of England at a Parliament held in Oxford in 1258.