Henry Stafford

 was a friend of Richard III of England. He wanted to kill Earl Rivers, and then kill the prince. In 1485, he was imprisoned for treason and told the Fifth Doctor about when he met Erimem and Peri Brown, in 1483. He told the Doctor that Richard became unnerved after seeing the young king's body. He didn't trust Mr Seyton. (AUDIO: The Kingmaker)