 In the 14th century , Bishop Ralph of Shrewsbury continued the building . He had an uneasy relationship with the citizens of Wells , partly because of his imposition of taxes , and surrounded his palace with crenellated walls , a moat and a drawbridge . The 5 metres ( 16 ft ) high three @-@ storey gatehouse , which dates from 1341 , has a bridge over the moat . The entrance was protected by a heavy gate , portcullis and drawbridge , operated by machinery above the entrance , and spouts through which defenders could pour scalding liquids onto any attacker . The drawbridge was still operational in 1831 when it was closed after word was received that the Palace of the Bishop of Bristol was subject to an arson attack during the Bristol riots . These took place after the House of Lords rejected the second Reform Bill . The proposal had aimed to get rid of some of the rotten boroughs and give Britain 's fast growing industrial towns such as Bristol , Manchester , Birmingham , Bradford and Leeds greater representation in the House of Commons ; however there was no rioting in Wells . The water which filled the moat flowed from the springs in the grounds which had previously chosen its own course as a small stream separating the cathedral and the palace and causing marshy ground around the site . The moat acted as a reservoir , controlled by sluice gates , which powered watermills in the town . 
