The Key to Time (box set)

The Key to Time is the umbrella title that links all six serials of Season 16 of Doctor Who. The arc was originally conceived of by producer Graham Williams, who had proposed it as part of his application for the producer's job in 1976. The name refers to the powerful artifact whose segments the Doctor, Romana and K-9 are searching for during the season.

A figure calling himself the White Guardian commissions the Doctor and K9, assisted by a new companion, the Time Lady Romana, to find the six segments of the Key to Time, a cosmic artifact resembling a perfect cube that maintains the equilibrium of the universe. Since it is too powerful for any single being to possess, it has been split into six different segments and scattered across space and time, disguised by the raw elemental power within them into any shape or size. However, since the forces balancing the universe are so upset, the White Guardian needs to recover the segments of the Key to stop the universe so that he can restore the balance. The White Guardian also warns the Doctor of the Black Guardian who also wishes to obtain the Key To Time for his own purposes.

The first segment is disguised as a lump of Jethryk on the planet Ribos. The second is the planet Calufrax, shrunk to miniature size by the space-hopping pirate planet Zanak. The third is the Great Seal of Diplos, which has been stolen by a criminal of that planet. The fourth is part of a statue on the planet Tara. The fifth has been consumed by the squid Kroll, causing it to turn into a gigantic monster. The final segment is a female humanoid — Princess Astra.

In the final episode, the Black Guardian, disguised as the White Guardian, attempts to take the Key from the Doctor. However, the Doctor sees through the figure's charade and orders the segments of The Key to Time to once again become scattered across all of time and space, bar the sixth, which he reinstates as Princess Astra.

The complete running time for all six serials in the arc is 633 minutes.

The Black Guardian returns in the three serial arc, "The Black Guardian Trilogy" The Black Guardian Trilogy involving the 5th Doctor and Vislor Turlough.

The Key to Time is available on DVD in North America and was released on region 2 (Europe) DVD on September 24, 2007.

Key 2 Time is a series of CD audio plays released by Big Finish Productions. Over the course of three stories, the Fifth Doctor must hunt down the redistributed segments of the Key, which are decaying the dimensions around them. The Doctor soon discovers the decay is a direct result of his actions in the first search for the Key, his attempt to assemble the Key using a makeshift sixth segment disrupting the balance between the segments and causing them to decay. The story ends with the Key being reassembled and the Doctor subsequently destroying the Key in the Chaos Pool where it was first made, undoing the damage it has caused and preventing anything from ever using the Key again. The three stories are The Judgement of Isskar, The Destroyer of Delights and The Chaos Pool.