London, 1966 - when the TARDIS materialises outside the Post Office Tower the Doctor becomes aware of a powerful and evil force nearby, so he and the ever-curious Dodo set off to investigate.

Inside the tower they track down the source of power to Professor Brett and WOTAN, his revolutionary new computer.

Designed as a universal problem solver, WOTAN has suddenly begun to think for itself and has formulated a deadly plan. Using its phenomenal power it will programme humans to build mobile fighting computers, and with these indestructible war machines WOTAN will take over the world...

Novelization of the Doctor Who TV series; four episode story "The War Machines" (1966), script by Ian Stuart Black.