Cyber-invasion (Silver Nemesis)

In the year 1988, the Cybermen attempted to invade Earth. (TV: Silver Nemesis)

Behind the scenes

 * The Discontinuity Guide implies that the "CyberIsomorphs" were infact native to the 20th century, descended from the Cybermen whom left Mondas. It was after they learnt of Mondas' destruction that they attempted to turn Earth into a new base planet.