<p>PeterCapaldi’sfinalepisodeofDoctorWhothisChristmaswillfeaturePearlMackieasBillPottsandbecalledTwiceUponaTime,itwasrevealedthisevening(23July)duringacastpanelatSanDiegoComicCon.ViewerswillhavetowaituntilChristmastodiscoverexactlyhowBill,whowillappearthroughouttheepisode,makesherreturn.</p>
