 In the expectation of a siege , the castle garrison was increased to around 800 soldiers ; the avenue of trees outside the castle gates were cut down , and neighbouring buildings destroyed to avoid them being used by Parliamentary forces . Large amounts of food were brought in to support the growing castle community , which also included a number of the wider Herbert family and other regional Royalist leaders who had sought shelter there . The first Parliamentary army arrived in early June , under the command of Colonel Morgan and Sir Trevor Williams . After several calls for the castle to surrender , a siege ensued , lasting through the summer months . In August , additional Parliamentary forces under General Fairfax arrived , and calls for the castle to surrender were renewed . Fairfax 's men began to dig trenches towards the castle , and used these to move mortars forward , probably including the famous " Roaring Meg " , bringing the interior of the castle into artillery range . Facing a hopeless situation , the Marquess surrendered the castle on 19 August on relatively generous terms for the garrison . The Marquess himself was arrested and sent to Windsor Castle , where he died shortly afterwards . 
