17–26 April – Second Barons' War: de Montfort besieges
Rochester Castle in Kent but fails to take it.[8]
14 May – Second Barons' War: the
Battle of Lewes is fought between Simon de Montfort and King Henry III in
Sussex. By the end of the battle, Montfort's forces capture both King Henry and his son, Prince
Edward, and Henry is forced to sign the
Mise of Lewes making Montfort the "uncrowned king of England".[3]
June – Simon de Montfort summons a parliament in London, the first to include
Knights of the Shire.
17 June – A fire destroys many of the wooden houses in the city of
Gloucester.[9]
4 August – Second Barons' War: The
Battle of Evesham is fought in
Worcestershire, with the army of Edward defeating the forces of rebellious barons led by Simon de Montfort and killing Montfort and many of his allies.[3]
16 September – Second Barons' War: Henry
disinherits all rebels against his rule.[1]
1266
June – Second Barons' War: Henry III besieges the rebels in
Kenilworth Castle.[1]
31 October – Second Barons' War: The war winds down as supporters of the slain rebel leader Simon de Montfort make an offer of peace to the king in the
Dictum of Kenilworth.[3]
19 November – the
Statute of Marlborough is passed, confirming
Magna Carta and the Provisions of Westminster. It is the oldest English law still (partially) in force.[10]
Roger Bacon completes his work Opus Majus and sends it to
Pope Clement IV, who had requested it be written; the work contains wide-ranging discussion of
mathematics,
optics,
alchemy,
astronomy,
astrology and other topics, and includes what some believe to be the first description of a
magnifying glass. Bacon also completes Opus Minus, a summary of Opus Majus, later in the same year.
^Lawrence, C. H. (1984). "The University in State and Church". In Aston, T. H.; Catto, J. I. (eds.). The History of the University of Oxford. Vol. 1. Oxford University Press.
^Huscroft, Richard (2006). Expulsion: England's Jewish Solution. Stroud: Tempus. p. 105.
ISBN9780752437293.
^Fogle, Lauren (2019). The King's Converts. Lanham, MD: Lexington Books. p. 40.
ISBN9781498589215.
^Cartwright, Mark.
"Rochester Castle". World History Encyclopedia. Retrieved 2021-05-07.
^Walford, Cornelius, ed. (1876). "Fires, Great". The Insurance Cyclopeadia: Being an Historical Treasury of Events and Circumstances Connected with the Origin and Progress of Insurance. C. and E. Layton. p. 27.