Gascon leaders travel to England to put their case against Simon de Montfort, who eventually resigns.
1253
6 August – Expedition by Henry III to Gascony to repel a rumoured invasion from Castile. Eleanor of Provence is regent and de facto Lord Chancellor in England during her husband's absence.
August – A gold penny is introduced, but swiftly withdrawn when its bullion value proves greater than its twenty pence face value.
c. September – 1257 Samalas eruption: Mount Samalas volcano erupts on Lombok Island in Indonesia; the resultant climatic changes combine with a second successive poor grain harvest this summer in Britain to produce famine, killing an estimated 17,000 in Britain (15,000 in London).
Brothers of Penitence (Fratres Saccati, 'Brothers of the Sack') first settle in England, in London.