Regeneration Impossible (audio story)

 was the fifth story of the tenth season of Big Finish Productions' Short Trips series.

Publisher's summary
The Doctor is in his TARDIS atop a cloud above Victorian London. He’s retired, no longer interfering in the affairs of others. There’s nothing that could make him help anyone else. Except, perhaps, the lure of another Time Lord...

The Doctor is locked in a mortuary in Victorian London, dying. He can’t escape and doesn’t know how to keep himself alive. Just when he thinks it can’t get any worse, he finds himself locked in with the one person he hates most in the entire universe.

Himself.

Plot
to be added

Characters

 * Eleventh Doctor
 * Twelfth Doctor
 * Gregory Chapman

Continuity

 * The Eleventh Doctor mistakes the Twelfth Doctor for the Master. (TV: Terror of the Autons, etc) The Twelfth Doctor scoffs at the suggestion, saying that she's "locked up 120 years and miles away." (TV: Extremis)
 * The Eleventh Doctor learns that he is to save Gallifrey. (TV: The Day of the Doctor)
 * The Twelfth Doctor refers to his past association with UNIT. (TV: The Invasion, etc)
 * Gregory Chapman uses a Time Ring. (TV: Genesis of the Daleks, Revenge of the Cybermen)
 * The Eleventh Doctor believes he is the last incarnation of his regeneration cycle. (TV: The Time of the Doctor, PROSE: Four Doctors)
 * The Eleventh Doctor decides to leave the TARDIS behind to investigate the possibility of another Time Lord, saying that the last time he took the TARDIS, she nearly became dinner. (TV: The Doctor's Wife)
 * The Eleventh Doctor says that regenerating in a morgue is something "you only do once". (TV: Doctor Who)
 * The Twelfth Doctor says his regeneration number is "complicated". (TV: The Day of the Doctor, The Time of the Doctor)
 * The Twelfth Doctor says that an old friend of his once told him that "you just have to save someone". (TV: The Fires of Pompeii)
 * The Twelfth Doctor psychically shows the Eleventh Doctor scenes from the latter's future: destroying the Dalek ship at Christmas (TV: The Time of the Doctor); his regeneration into the Twelfth Doctor (TV: The Time of the Doctor); him telling Clara that she can't see him (TV: Deep Breath); and him calling himself "the man who stops the monsters." (TV: Flatline)
 * When asked if the Twelfth Doctor knows any psychopaths with a penchant for the convoluted, he replies that he knows two - he locked one in his basement and married the other.
 * The Twelfth Doctor says "here we go again" as he regenerates. The phrase was previously said by the Brigadier (TV: Planet of the Spiders) and Madame Vastra (TV: Deep Breath), also in response to the Doctor's regenerations.
 * The Doctors deduce that the trap had to go after the Twelfth Doctor because his current career as a professor marked the only time when a Time Lord remained in one place for a prolonged period with a full set of regenerations and access to a working TARDIS, conditions that don't apply to his time in UNIT and the Eleventh's current 'retirement'.
 * The Eleventh Doctor mentions watching his own death before with a spacesuit coming out of a scenic lake. (TV: The Impossible Astronaut)
 * The Eleventh Doctor says "Why did he have to be old? Anything but old!" when referring to his future self, mimicking his own words to Clara over the telephone before he regenerated. (TV: Deep Breath)
 * The Twelfth Doctor is aware of Bill sneaking into his lectures (TV: The Pilot)
 * After having his mind erased, the Eleventh Doctor wonders if he's ginger. (PROSE: Battlefield, The Tomorrow Windows; TV: The Christmas Invasion, The End of Time)