The Mind Robber

From http://www.bbc.co.uk/doctorwho/classic/episodeguide:

To escape from the volcanic eruption on Dulkis, the Doctor uses an emergency unit which moves the TARDIS out of normal time and space. The travellers find themselves in an endless void, where they are menaced by White Robots.

Having regained the safety of the TARDIS, they believe they have escaped - until the ship suddenly explodes apart. They then find themselves in a land of fiction, where they are hunted by life-size clockwork soldiers and encounter characters like Rapunzel and Swift's Lemuel Gulliver.

This domain is presided over by a man known only as the Master - a prolific English writer from 1926 - who in turn is controlled by a Master Brain computer. Now the Master is desperate to escape and wants the Doctor to take his place, while the Master Brain plans to take over the Earth.

The Doctor engages the Master in a battle of wills using a variety of fictional characters. Zoe and Jamie meanwhile succeed in overloading the Master Brain and, in the confusion, the White Robots destroy the computer, finally freeing the Master.

5 out of 118 (4.2%) raters say this story requires a previous story.