Battle of Battersea Power Station

On a parallel Earth, the Battle of Battersea Power Station was a major battle in London between the Cybermen and the resistance group known as the Preachers as well as the Tenth Doctor and his companions.

It ended when the Doctor shutdown the Emotional inhibitor of all the Cybermen, causing them to explode. The Cyber-Controller fell into the exploding power station, (TV: The Age of Steel) while the remaining Cybermen were then sealed in the factories. (TV: Doomsday) It would serve as the first major conflict of a war that would finally end at the Battle of Canary Wharf in the Doctor's world. (TV: Army of Ghosts / Doomsday)

Origins
In the parallel universe known as Pete's World, John Lumic became obsessed with immortality and thus began creating the Cybermen with the plan to eventually transform himself into one. A small resistance group known as the Preachers led by Ricky Smith rose up to combat him and his efforts while Pete Tyler acted as a loyal friend to Lumic but in reality recognised his insanity and sent information to the Preachers under the alias Gemini, believing them to be security forces. In order to create more Cybermen, Lumic would trick homeless people desperate for food into getting into lorries and then kidnap them to be Cyber-converted as they wouldn't be missed.

Lead up to the battle
After the president refused to fund his work, Lumic initiated his plans for a war footing, using the pre built Cybermen to assassinate the president at Jackie's birthday party. (TV: Rise of the Cybermen) Once done, he had the ear pieces activated to control the residents of London to go to the power station to await conversion. However, unbeknownst to him, the Tenth Doctor, Pete Tyler, Rose Tyler and the Preachers had evaded capture as the Doctor successfully destroyed the group of Cybermen that pursued them with a TARDIS circuit. A further group in the main city attempted to capture them but only succeeded in killing Ricky Smith with their electric hands, unable to reach Mickey Smith. (TV: The Age of Steel)

The remaining group eventually reunited across from the power station, the Doctor having worked out that was were Lumic's transmitter was located. They decided to attack on three fronts: Mickey and Jake would infiltrate the Zepplin and shut down the transmitter, Rose and Pete would use fake ear pods to join the crowd of people lining up for an upgrade in the hopes of finding Jackie while the Doctor and Mrs Moore would sneak in under the factory where all the Cybermen in status were kept. (TV: The Age of Steel)

Meanwhile Crane, Lumic's right hand man, refused to comply with Lumic's desire for a world of Cybermen. Ensuring he would be brought to Lumic, he used their friendship to enable him to get close enough to Lumic to severely damage his life support. However, the Cybermen deleted him for doing so. Understanding Lumic was close to death, the Cybermen sped up his conversion and forced him to the chambers despite his protests. (TV: The Age of Steel)

Breaking in
The Doctor and Moore managed to reach the inside of the factory, narrowly avoiding the awakened Cybermen. While searching the base, they found a Cyberman, Moore disabling it with an EMP. Upon inspecting the disabled Cyberman, the Doctor worked out that destroying the emotional inhibitor was the way to defeat them, though it would kill all the humans inside as well. However, Moore was killed by another Cyberman, the Doctor being captured as his Binary vascular system made him worthy of inspection by Lumic, now upgraded as the Cyber-Controller.

Meanwhile, Rose and Pete made it deep into the station only for Pete to be recognised by one Cyberman, who claimed she was the converted Jackie Tyler. The revelation surprised the pair enough they displayed emotion, being taken away to the Cyber-Controller also. Elsewhere, Mickey and Jake knocked out the guards guarding the Zepplin (as Mickey was against shooting them) and found the transmitter in the control deck of the Zepplin. However, they struggled to disable it, eventually using a Cyberman who activated to protect the room to punch it for them, disabling it while also destroying the Cyberman. As such, the humans below realised where they were and fled, the sheer numbers being too much for the Cybermen to stop. Mickey then hacked into the station's cameras, enabling him to see Pete, Rose and the Doctor being confronted by the newly converted Cyber-Controller.

Defeating the Cybermen
The Doctor openly chastised the Cyber-Controller for his actions, stating it was not true evolution and that his creation lacked the one thing that had led him to make them; imagination. The Cyber-Controller dismissed him, stating he would convert everyone to make "a world without pain". The Doctor, having deduced Mickey was watching, crytically informed him about the Cybermen's emotional inhibitor and to find the code to deactivate, appearing to merely be rambling to the Cyber-Controller. Having found the code, Mickey messaged it to Rose via her phone, who then tossed it to the Doctor, who plugged it into the Cyber-net's mainframe. Since Lumic had made their technology able to connect with all electronics, the code was instantly downloaded into the Cybermen, causing them to cry out and destroy themselves.

The group then fled through the exploding station to the roof, where Mickey and Jake sent down a set of ladders so they could climb up to the Zepplin as they took off. However, the Cyber-Controller (unaffected by the code) had pursued them, clinging onto the rungs. Pete, using the Doctor's Sonic screwdriver, disconnected the lower end of the ladder, sending the Cyber-Controller down into the burning building, killing him. (TV: The Age of Steel)

Aftermath
The Doctor and Rose left the world to return to their own earth, leaving Mickey behind, who desired to stay and fight with Jake to ensure Cybermen throughout the world were defeated also. The Doctor also informed Jake that Moore was actually called Angela Price, giving the man the task to find her family and inform them about her sacrifice. (TV: The Age of Steel)

Pete Tyler eventually became heavily involved in the war that soon occurred. The Cybermen were successfully sealed in their factories and the world began to debate over what could be done to help them. Eventually, the Cybermen hacked into the Torchwood of that world and fled through the Void to the Doctor's world, leading to a conflict at Canary Wharf. (TV: Doomsday)