The Pursuit of History (audio story)

 was the seventh story in the fifth series of The Fourth Doctor Adventures, produced by Big Finish Productions. It was written by Nicholas Briggs and featured Tom Baker as the Fourth Doctor, Lalla Ward as Romana II, John Leeson as K9 Mark II, David Warner as Cuthbert, Toby Hadoke as Mr Dorrick, David Troughton as The Black Guardian and introduced Jez Fielder as The White Guardian.

It was followed by the concluding story ''Casualties of Time.

Publisher's summary
On a brisk winter's morning in 1850s Yorkshire, Cuthbert, head of the intergalactic business known as "The Conglomerate" prepares to hijack a very special train.

In the far future, his assistant, Mr Dorrick is awoken by howling alarms. There is a problem with the Quantum Gateway.

In the TARDIS, the Doctor, Romana and K9 detect strange distortions in the Vortex, an energy stream coming from a strange creature called a Laan.

The threads of a plan centuries in the making are coming together. But who is behind this plan? And can anyone possibly escape when history is against them?

Part one
to be added

Part two
to be added

Cast

 * The Doctor - Tom Baker
 * Romana - Lalla Ward
 * K9 / The Oortag - John Leeson
 * Cuthbert - David Warner
 * Mr Dorrick - Toby Hadoke
 * Mr Edge - David Troughton
 * David Goddard / Oceanic Airforce Commander - John Dorney
 * Conglom-Net Computer / Oceanic Airforce Pilot - Lisa Bowerman
 * Neville Sanders / Drudger / Ecidien Cerebus Bird / Albert Chatterton / The White Guardian / Salonu Prime - Jez Fielder
 * The Laan / Salonu - Jane Slavin

Crew

 * Cover Art - Anthony Lamb
 * Writer & Director - Nicholas Briggs
 * Executive Producers - Jason Haigh-Ellery and Nicholas Briggs
 * Music and Sound Design - Jamie Robertson
 * Producer - David Richardson
 * Script Editor - John Dorney

Worldbuilding

 * The Salonu use nitrogen-rich atmospheres to refuel their ships via nitrogen conversion.
 * Cuthbert's train robbery occurs in Yorkshire on 15 November 1859.
 * Miles of heathland were transplanted into the TARDIS.
 * The Laan are a spatio-temporal nomadic species.
 * When K9 detects an energy stream, the Doctor suggests it's the Laan's space-time spore.
 * In 1859, Victoria is on the throne of Great Britain and Ireland and A Tale of Two Cities is published.
 * On 15 November 1859, there were exactly 1,000,300,558 human beings on Earth.
 * The Oortag Leader, more commonly referred to as "Oortag," is an Oortag. The Conglomerate helps them with healthcare and education.
 * Romana arrives on space platform 237, which is part of the 552,000 space platforms that make up the time engine. The time engine powers the Quantum Gateway which sustains the Conglomerate.
 * Cuthbert plans to irradiate tritonium in 1859, making it valuable by 2059.
 * In 2059, the Oceanic States, suffering from under-investments in healthcare, education, and defence, is part of the "volatile international situation" with the Asiatic States.
 * The Time Lords are the most powerful time sensitive race the universe has ever known.
 * Romana describes a causal loop, or causal historical loop, as a self-sustaining historical paradox.

Continuity

 * K9 and Romana locate the avian life form in the TARDIS. (AUDIO: The Sands of Life, The Trouble with Drax)
 * The Ecidien Cerebus Bird repeats "About time I found something better to do than run round after the Brigadier" (TV: Pyramids of Mars) and "I'm afraid it's none of my business. I suggest you leave here." (TV: An Unearthly Child)
 * Romana refers to the miles of heathland and the Bird as being "at the heart of the TARDIS." (TV: Terminus, Doctor Who)
 * The Doctor checks the helmic regulator. (TV: The Ark in Space)
 * The Doctor and Romana previously encountered Cuthbert, the Conglomerate and the Quantum Gateway in the Proxima System. (AUDIO: The Dalek Contract / The Final Phase)
 * They previously encountered the Laan when they first met Cuthbert, and a Laan once again calls to Romana. (AUDIO: The Sands of Life / War Against the Laan)
 * The Doctor overrides the randomiser. (TV: City of Death, The Creature from the Pit, AUDIO: The Trouble with Drax)
 * The planet Vulcan was discovered in 1859. (TV: The Power of the Daleks)
 * K9 assimilated information from the Bi-Al Foundation genealogical database. (TV: The Invisible Enemy)
 * There is a "volatile international situation" between two powers. (TV: Warriors of the Deep)