The siege of Kenilworth Castle in 1266 was "probably the longest in English history" according to historian Norman Pounds, and at the time was also the largest siege to have occurred in England in terms of the number of soldiers involved.[63] Simon de Monfort's son, Simon de Montfort the Younger, promised in January 1266 to hand over the castle to the king. Five months later this had not happened, and Henry III laid siege to Kenilworth Castle on 21 June.[64] Protected by the extensive water defences, the castle withstood the attack, despite Edward targeting the weaker north wall, employing huge siege towers and even attempting a night attack using barges brought from Chester.[65] The distance between the royal trebuchets and the walls severely reduced their effectiveness, and heavier trebuchets had to be sent for from London.[65] Papal intervention through the legate Ottobuono finally resulted in the compromise of the Dictum of Kenilworth, under which the rebels were allowed to re-purchase their confiscated lands provided they surrendered the castle;[66] the siege ended on 14 December 1266.[67] The water defences at Kenilworth influenced the construction of later castles in Wales, most notably Caerphilly.[68]