John of England

King John of England was most notable for signing the Magna Carta in 1215.

While the real King John was in London taking the Crusader's Oath on 4 March 1215, the android Kamelion was being used in a plot by the Master to sabotage Earth history by preventing King John's signing of the Magna Carta, an event pivotal to the development of parliamentary democracy on that planet. The plot was foiled by the intervention of the Doctor. (DW: The King's Demons)

Earlier in his personal timeline, the Doctor had met John's elder siblings Richard the Lionheart and Princess Joanna in Palestine during the Third Crusade. (DW: The Crusade)

Behind the scenes
The following year, whilst eluding rebel forces, John sent his baggage train across the square-mouthed estuary on the northwest margin of East Anglia, only to have the Crown Jewels it carried accidentally dropped and sunk in its waters. Tegan Jovanka's foreknowledge of this event was summed up in her assessment of John as "the one who lost something in ."