How the heck did Danny Pink and the Brig reverse full Cyberman conversion in “Death in Heaven“? Most failures were during the conversion process (Toberman “Tomb of the Cybermen“, Commander Lytton “Attack of the Cybermen“, Mercy Hartigan “The Next Doctor“, the Doctor “Nightmare in Silver“, Craig Owens “Closing Time“). The only pre-“Death in Heaven” full-conversion failure I can think of is Yvonne Hartman in “Doomsday“.
The No-Prize Solution
Steven Moffat never specified where the material to build the new Cybermen came from. They were obviously built in a hurry with faulty material, allowing a higher failure percentage. To put it another way, they don’t make Cybermen like they used to.