Queen M

Queen M was a character who was portrayed by Sonia Hieny in the 1954 film Tricky Dicky!, an adaptation of William Shakespeare's play Richard III. (COMIC: The Good Soldier) Henry VI was the King of England for several decades during the Wars of the Roses, when the play was set. (AUDIO: The Kingmaker)

Behind the scenes
Queen M is clearly a fictionalised version of, a Queen of England during the Wars of the Roses as the consort of Henry VI, though Richard III is set after his death. Although The Kingmaker falls short of explicitly identifying Henry's Queen, its references to Shakespeare's play do suggest it was accurate enough for Margaret to be a real person within the Doctor Who universe.