Invasion of the Dinosaurs. Exact date is conjecture. The man says that King Richard is away at the Crusades. A medieval knight from this era is pulled forward through time by the Master to attack a UNIT convoy. The Time Monster.
Exact date is conjecture.
Williams' cousin, Sir Geoffrey de Lacey, is summoned to London in order to take the Crusader's Oath with King John in a week. He has the shape-changing robot, called Kamelion, under his power assume the role of King John and behave erratically. The 5th Doctor, Tegan and Turlough arrive and are able to expose the imposter, taking Kamelion with them when they leave. The Magna Carta is sealed by King John at Runnymead, England. 1252 Marco Polo is born.