The Auton Infinity (audio story)

 was the only story in the audio anthology Forty: Volume 2. It was written by Tim Foley and featured Peter Davison as the Fifth Doctor, Janet Fielding as Tegan Jovanka, Mark Strickson as Turlough and Jon Culshaw as Kamelion, Brigadier Lethbridge-Stewart and.

Publisher's summary
Snowdonia. UNIT is running a training exercise with the Brigadier in attendance. Except it isn’t long before things start to go badly wrong. The fake aliens primed to attack the troops might not be so fake after all, and a temporal disturbance attracts the Doctor, Tegan and Turlough into the fray.

Old enemies are on the scene with a deadly plan - but they might be the least of the Doctor's worries.

Because he's recently been sent backwards and forwards through his own lifetime...and he’s finally going to find out why.

Plot
to be added

Cast

 * The Doctor - Peter Davison
 * Tegan Jovanka - Janet Fielding
 * Turlough - Mark Strickson
 * Kamelion / Brigadier Lethbridge-Stewart / - Jon Culshaw
 * Prodigal - Juliet Aubrey
 * Veronica Holmes - Lucy Fleming
 * Captain Ted Mears - Oscar Pearce
 * Sergeant Janet Wharry - Fiona Hampton
 * Corporal Vikram Plamer - Homer Todiwala
 * Dobson / The Autons - Glen McCready

Uncredited Cast

 * Auton Doctor - Peter Davison
 * Peri Brown - Nicola Bryant

Continuity

 * The Brigadier has still officially retired from UNIT. (TV: Mawdryn Undead, The Five Doctors, Battlefield)
 * The TARDIS is still being drawn to the middle of the universe. (TV: Frontios)
 * "The Brigadier" refers to Charles Crichton. (TV: The Five Doctors)
 * The Doctor refers to the Gravis. (TV: Frontios)
 * Tegan believes the Doctor is still missing the Sonic Screwdriver. (TV: The Visitation)
 * UNIT had previously served as security for peace conferences in TV: The Mind of Evil and Day of the Daleks.
 * Turlough is embarrassed about the idea of driving in the Brigadier's presence, with the Brigadier still upset with him for crashing his own car. (TV: Mawdryn Undead)
 * The Doctor reminds Turlough that the Brigadier taught him at Brendon Public School. (TV: Mawdryn Undead)
 * Captain Mears refers to London being invaded by the Yeti (TV: The Web of Fear), dinosaurs (TV: Invasion of the Dinsaurs) and the Loch Ness Monster. (TV: Terror of the Zygons)
 * The Master previously formed an alliance with the Autons in TV: Terror of the Autons. He reacquainted with them on the Death Zone on Gallifrey. (TV: The Five Doctors)
 * The Doctor wonders if the military is being run by Rowlands (TV: Terror of the Autons) and Horatio Chinn. (TV: The Claws of Axos)
 * The Master doubts he would become a woman. Later in his timeline, he would regenerate into his Missy incarnation. (TV: Deep Breath, et al)
 * The earlier Doctor has just encountered the Cybermen on Telos (AUDIO: Secrets of Telos) and the Ice Warriors. (AUDIO: God of War)
 * Tegan recalls the Tomb of Rassilon. (TV: The Five Doctors)
 * The Brigadier's memories of the Tomb of Rassilon are vague. Turlough theorises that the Time Scoop bringing the Doctor's companions out of their timeline had affected their memories. (TV: The Five Doctors)
 * Turlough tells the Brigadier about his alliance with the Black Guardian. (TV: Mawdryn Undead to Enlightenment; AUDIO: Gardens of the Dead)
 * The earlier Doctor remembers Tegan and Nyssa telling him about Adric's death, an event in his personal future. (TV: Earthshock, AUDIO: Secrets of Telos)
 * Tegan recalls the Doctor feeling the effects of his past incarnations being taken out of time by the Time Scoop. (TV: The Five Doctors)
 * The Brigadier was unaware that Turlough was from another planet. (TV: Mawdryn Undead, Planet of Fire)
 * Whilst reading Tegan's mind, Prodigal sees the day she met the Doctor on the day her aunt Vanessa died (TV: Logopolis) and encountering the Cybermen (TV: Earthshock, The Five Doctors; AUDIO: Secrets of Telos, Conversion)
 * The Master refers to the Martian Pyramids. (TV: Pyramids of Mars)
 * The Doctor hopes the Brigadier doesn't end up on Nerva Beacon. (TV: The Ark in Space, Revenge of the Cybermen)
 * The future Doctor still has possession of the Seal of Rassilon, which his third incarnation took from the Master in the Death Zone. (TV: The Five Doctors)
 * The TARDIS previously became an empty shell in TV: The Wheel in Space. It would do so again in TV: Father's Day.
 * The Doctor refers to the Brigadier as "the original, you might say." (TV: The Five Doctors, The Doctor Falls, Twice Upon a Time)
 * The Doctor refers to the Arc of Infinity. (TV: Arc of Infinity)
 * Tegan recalls Nyssa collapsing after leaving the Urbankan ship. (TV: Four to Doomsday)