Doomsday bomb

The doomsday bomb was a superweapon kept in Earth's secret weapons store. A force of Cybermen used the Cyber-Mole to drill beneath London into the Earth's secret weapons store to steal the doomsday bomb. They achieved this and held the world ransom with the bomb. The Second Doctor brought his information on Cybermen to the military and lead an assault on the Cyber-Mole using anti-Cybermen weapons, defeating them. (TVC: Cyber-Mole)