Battle of Lewes 1264 On 14th May 1264 Simon de Montfort's army of 5000 Barons and Londoners defeated royalist forces of twice that size under Henry III on the Downs northwest of Lewes. The Mise of Lewes, signed next day led to the first English parliament meeting at Westminster 20th January, 1266. This viewing platform was erected by Lewes Town Council and unveiled by the Mayor Councillor R.H Yarrow M.B.E. on 14th May 1985.