Robot knight (Robot of Sherwood)

A group of robots who masqueraded as a force of medieval knights travelled aboard a spaceship, observed by the Twelfth Doctor to have came from the 29th century, which had crash landed on Earth in the past while on a destination to the Promised Land. The ship surfaced as the castle of Nottingham in 12th century England. By this point, they served the Sheriff of Nottingham, who aspired to take the English throne. Most were destroyed by the Twelfth Doctor, Maid Marian and a peasant uprising, but at least two survived to flee in their ship. Knowing the ship was too damaged to make it to orbit, the Doctor, Robin Hood and Clara Oswald fired a golden arrow into the ship's engine, giving it enough of a boost to reach orbit where it exploded harmlessly, destroying the last of the robots. (TV: Robot of Sherwood)

After the Twelfth Doctor's mind was connected to a mind scythe, the "holiday snaps" the Doctor showed Kygon Brox included a robot knight. (COMIC: The Instruments of War)