The Martian Invasion of Planetoid 50 (audio story)

 was the fifth story in the Once and Future audio series, produced by Big Finish Productions in celebration of the 60th Anniversary of Doctor Who.

It was written by Jonathan Barnes and featured David Tennant as the Tenth Doctor, Stephen Noonan as the First Doctor, Michelle Gomez as Missy, Neve McIntosh as Madame Vastra, Catrin Stewart as Jenny Flint and Dan Starkey as Strax.

Publisher's summary
The Time War. The Doctor has been injured and brought to a Time Lord field hospital His body glows with energy, but this is no regeneration into a future form – instead, the Doctor’s past faces begin to appear as he flits haphazardly between incarnations…

Staggering to his TARDIS, the Doctor sets out to solve the mystery of his ‘degeneration’. Who has done this to him? How? And why? From the Earth to the stars, across an array of familiar times and places, he follows clues to retrace his steps, encountering old friends and enemies along the way. Tumbling through his lives, the Doctor must stop his degeneration before he loses himself completely...

The First Doctor arrives in Victorian London amid a Martian invasion. But he discovers all is not what it seems when Missy appears…

Soon, the Doctor is propelled into a future incarnation – the Tenth – but he is not alone in battling Missy and her Martian invaders. The Paternoster Gang – Madame Vastra, Jenny Flint and Strax – are also here to assist. But can they offer the Doctor any help in solving his own degeneration mystery?

Plot
to be added

Cast

 * The Doctor - David Tennant
 * Missy - Michelle Gomez
 * Madame Vastra - Neve McIntosh
 * Strax - Dan Starkey
 * Jenny Flint - Catrin Stewart
 * The First Doctor - Stephen Noonan
 * The Third Doctor - Tim Treloar
 * Jessamy Moore - Hannah Genesius

Worldbuilding
to be added

Continuity

 * Strax recalls the Doctor at Demons Run. (TV: A Good Man Goes to War)
 * The Doctor farewells the future body by saying: "But now, I do want to go." (TV: The End of Time, The Day of the Doctor)
 * Strax refers to the Eleventh, Twelfth and Thirteenth Doctors. Though he believes the latter to be a boy, given his confusion of humanoid genders.