The walls were partially rebuilt in the 14th century , and the upper parts of the walls date from this time . A chapel was added to the south side of the building in the 16th century . A vault under the south chapel was used to bury members of a local family , the Pierce Lloyds . In 1999 , the vault was used to record some " atmospheres " for the album " You Have Just Been Poisoned By The Serpents " by The Serpents , a collective of Welsh musicians including members of Echo and the Bunnymen , Super Furry Animals and Ectogram that was described by one journalist as " possibly the strangest pop group of all time " .