Thomas Becket was an English priest , and Archbishop of Canterbury , who was assassinated by four knights in Canterbury Cathedral in 1170 . People used to think his name was Thomas Ã Becket , but it is now known to be wrong . Thomas Becket ( 1118 â `` 29 December 1170 ) , later also known as Thomas Ã Becket , was Archbishop of Canterbury from 1162 until his murder in 1170 .