Survival of the Fittest (audio story)

 was the one hundred and thirty-first monthly Doctor Who audio release produced by Big Finish Productions. It is the final 3 part story in Big Finish's Doctor Who range, bringing the experiment of 3 and 1 part stories, beginning in April 2007 with I.D. (3 part) and Urgent Calls (1 part), to a close.

Publisher's summary
The hive of the Vrill bears the scars of a terrifying cataclysm. Only a handful remain alive, hatched after the holocaust of the mysterious Winterlack. The Vrill seek a new Authority. They find the Doctor, a two-legged creature who can lead them to survival. He must solve the mystery of the Carrion beast that haunts the lower chambers. He must face the Winterlack that still stalk the mountains. And he must find a path that does not lead to extinction...

Plot
to be added

Cast

 * The Doctor - Sylvester McCoy
 * Elizabeth Klein - Tracey Childs
 * Steffen / The Authority - Adrian Bower
 * Rose / The Vrill - Hannah Smith
 * Lilly / The Vrill - Evie Dawnay
 * Jackson / The Watcher - Mark Donovan
 * The Carrion - Alex Mallinson
 * Butterfly - Rupert Wickham

The Doctor

 * The Doctor tells Lilly that he has known many beekeepers in his time. He claims that Aristotle never stopped wittering on about bees whereas he was stuck at a tea party with Thomas Jefferson and he spoke about them at least.
 * Klein tells the Doctor that, with his intelligence, he would have been a great asset to the Nazi Party. The Doctor sarcastically remarks that it was "such a sweet thing to say."

Planets

 * The Doctor and Klein previously visited the crystal plains of Mandroxya, the Folly Ocean of Quindrax IV and the mercury swamps on Vulcan.

TARDIS

 * Through the TARDIS' telepathic circuits, Klein hears the Doctor speaking German in "a stuffy Prussian accent."

Continuity

 * The Doctor and Klein have recently visited the mercury swamps of Vulcan. (TV: The Power of the Daleks)
 * There no longer seems to be a spare TARDIS key in the cubbyhole above the "P" outside the TARDIS. (AUDIO: The Architects of History) It would be restored by the time of the Doctor's regeneration into his eighth incarnation. (TV: Doctor Who)