Osterhagen Project

The Osterhagen Key was a device that was held by UNIT by the time of the New Dalek Empire's invasion of Earth.

After Earth fell to the Daleks, General Sanchez of UNIT gave the key to Martha Jones along with the prototype of Project Indigo to escape. Former Prime Minister Harriet Jones told Martha Jones not to use the key under any circumstances. (DW: The Stolen Earth)

The purpose of the key is among UNIT's most closely guarded secrets, so much so that while Jack Harkness of Torchwood 3 was able to learn the details of another top-secret UNIT initiative, Project Indigo (among many other UNIT secrets), he has no knowledge of the key. (DW: The Stolen Earth)

Behind the Scenes
The actual spelling of the name of the key is unknown, but it has been pronounced differently during the episode DW: The Stolen Earth by various cast members. Throught the Dr Who series many device names have been anagrams of a devices purpose, or a clue to the plot put in by the producers. Some alternate spellings and anagrams based on the differing pronunciations have been suggested such as:-


 * "Osterhagen" - "Earth's Gone", perhaps a key to self-destruct the planet, or a saved backup of the Earth on the disk-like key to be used in the event of the planets destruction.
 * "Ostrhagin" - "Rani Ghost", suggesting The Rani is "ghosted" into the key in the same way cast members were ghosted into the space helmet communications systems in the episode DW: The Library
 * "Osterhaigen Key" - "Rose the key again", indicating once again Rose Tyler will be instrumental in defeating the Daleks.