 Boley Hill to the south of the castle may have been used as John 's headquarters during the siege . According to the Barnwell chronicler , five siege engines hurled a barrage of stones at the castle 's wall day and night . These were supported by missiles from smaller bows and crossbows . Though the Barnwell chronicler claimed they smashed a hole in the castle 's outer walls , Roger of Wendover asserted they were ineffective and that John turned to other methods to breach the defences . A letter dated 14 October indicates John was preparing to undermine the castle 's walls . He wrote to Canterbury , asking for the production " by day and night of as many picks as you are able " and that they be sent to Rochester . On 26 October a relief force of 700 horse was sent from London . They turned back before arriving , perhaps because they heard the king was advancing to meet them . 
