Clockwork soldier

The clockwork soldiers were giant, clockwork robots that appeared as toy soldiers, and were used for patrols in the Land of Fiction, used by the Master of the Land. (TV: The Mind Robber)

Characteristics
They were propelled by clockwork keys. (AUDIO: Legend of the Cybermen) The light on top of their hats was used as a camera for the Master of the Land to see from his base, and may have been motion sensitive. (TV: The Mind Robber, AUDIO: Legend of the Cybermen). At least during the war with the Cybermen, they often appeared with a jaunty military tune arriving their presence. They would attack if necessary with rifles tipped with sharp bayonets. Fictional characters inhabiting the Land of Fiction could not see them. (TV: The Mind Robber)

History
During the Mistress of the Land's war against the Cybermen, the Clockwork soldiers were used as the leasing front-line defence against the Cybermen-controlled White Robots in the White Void. They helped Zoe when she came again to the Land of Fiction and rescued Jamie McCrimmon from a group of White Robots. (AUDIO: Legend of the Cybermen)

Other references
In the video game Happy Deathday, played by Izzy Sinclair on the Time-Space Visualiser, a clockwork soldier was among a host of "every single enemy" that the Doctor had ever defeated, who were assembled by the Beige Guardian and pitted against the Doctor's first eight incarnations. (COMIC: Happy Deathday)