6 August – Expedition by
Henry III to Gascony to repel a rumoured invasion from
Castile.[3]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gold penny is introduced, but swiftly withdrawn when its bullion value proves greater than its twenty pence face value.[3]
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).[10][11]
Brothers of Penitence (Fratres Saccati, 'Brothers of the Sack') first settle in England, in London.[12]