The TARDIS arrives in London in 1966 and the Doctor (William Hartnell) and Dodo (Jackie Lane) visit the Post Office Tower. There they meet Professor Brett (John Harvey), whose revolutionary new computer WOTAN (Will Operating Thought ANalogue) can actually think for itself and is shortly to be linked up to other major computers around the world -- a project overseen by civil servant Sir Charles Summer (William Mervyn). It transpires however that WOTAN considers humans inferior to machines and should therefore be ruled by them. Exerting a hypnotic influence, it arranges the construction of War Machines -- heavily-armed, self-contained mobile computers -- with which to take over the world. These prove more than a match for troops, but by establishing a magnetic force field the Doctor is able to capture one of them, which he then reprograms to destroy WOTAN. Dodo, now back in her own time, decides to remain on Earth. The Doctor enters the TARDIS alone, but Brett's secretary Polly (Anneke Wills) and her merchant seaman friend Ben Jackson (Michael Craze) follow him inside just before it dematerializes!
This is item 11 in The Doctor Who: The First Doctor, William Hartnell (1963-1966) Series.