Black Archive

The Black Archive was a secret vault maintained by UNIT, later relocated to the Tower of London. The dangerous equipment it contained was such that even the Archive's own staff were forbidden to know what it held.

Function
It functioned as a depository of everything that shouldn't exist on Earth but did anyway, and required a UNIT level one clearance to gain entrance. (TV: Enemy of the Bane) The staff had their memories erased after every shift. (TV: The Day of the Doctor) In the event of alien invasion the contents of the Black Archive were deemed so dangerous that the nuclear warhead situated 20 feet beneath the archive was to be detonated in order to prevent the invading species from gaining access to the technology contained within the archive. (TV: The Day of the Doctor)

History
The Doctor, during either his second or third incarnation, aided in the foundation of the Black Archive. (COMIC: Don't Step on the Grass) At some point, UNIT started keeping a particular eye on the Doctor's companions. They kept a wall of photographs of the companions in the Black Archive. Clara Oswald, and perhaps others, was taken to the archive as part of this screening. Her memories of the visit were subsequently erased. (TV: The Day of the Doctor)

On 4 June 1972, UNIT bought the Tunguska Scroll from a private collector and placed it in the Black Archive. In 2009, Brigadier Lethbridge-Stewart smuggled Sarah Jane Smith into the archives to steal the scroll. (TV: Enemy of the Bane) During the same year, the Tenth Doctor sent Martha Jones there to fetch information on the Krynoid virus in the hopes that it might hold a key to stopping the Enochian invasion in Greenwich Park. (COMIC: Don't Step on the Grass) In the 21st century, a vortex manipulator had been donated to the archive by Captain Jack Harkness. A Zygon impersonating Kate Stewart took Clara there to retrieve it. Clara used the manipulator to escape the Zygon, and travel to 1562 to rescue three incarnations of the Doctor. Having free reign of the base, the Zygons believed that they could overrun the Earth easily with the amount of alien technology now in their possession. The real Kate Stewart then turned up however, and activated the nuclear armed self-destruction mechanism located under the base. The Zygon who was imitating Kate was able to shut off the device, which was keyed to respond to Kate's voice, but the real Kate could likewise countermand it. This resulted in a deadlock between the two. Eventually the Eleventh, the Tenth, and War Doctors arrived to stop her. They activated the memory erasing equipment in the ceiling, meaning the two sets of people forgot whether they were human or Zygon, and stopped the self-destruction mechanism. This saved themselves and the whole of London, also resulting in peace talks between the humans and the Zygons. (TV: The Day of the Doctor)

The archive was later the repository of the Osgood Box, which symbolized the peace between humans and Zygons. By this point in its history, the Doctor, along with both human and Zygon versions of Osgood, as well as the Doctor's then-companion Clara Oswald, were allowed to access the archive, with Clara apparently able to access the archive unquestioned, despite being a civilian. (TV: The Zygon Inversion)

Inventory
Its inventory included the Tunguska Scroll, stolen by Sarah Jane Smith in 2009, (TV: Enemy of the Bane) Magna-Clamps, the head of a Cyberman, the head of a Supreme Dalek, a pair of red heeled shoes, a Time Agent vortex manipulator donated by Jack Harkness, a space-time telegraph originally given to Alistair Gordon Lethbridge-Stewart by the Doctor, allowing direct communication to the TARDIS, a board containing photographs of the Doctor's past companions, a Dalek Tommy gun, a chair from the Naismith mansion, half part of a Silent, TARDIS coral, facemask of one of the Clockwork Droids, a pinwheel, a sonic probe, a Sontaran blaster, a damaged Dalek. (TV: The Day of the Doctor) and a Mire battle helmet. (TV: The Zygon Inversion)

Behind the scenes

 * In an interview after the broadcast of The Day of the Doctor, Steven Moffat revealed that the Black Archive was at one point also to house two movie posters for Dr. Who and the Daleks and Daleks' Invasion Earth 2150 A.D., which Clara was to have been seen examining, establishing the Peter Cushing films as existing within the Whoniverse. Unworkable rights fees prevented this from happening.
 * The Black Archive is also the title of a series of novella length critical monographs from Obverse Books. Each Archive entry focusses on a single serial from the show's entire history.