The Doomsday Chronometer (audio story)

 was the third story in the audio anthology Doom Coalition 3, produced by Big Finish Productions. It was written by Matt Fitton and featured Paul McGann as the Eighth Doctor, Nicola Walker as Liv Chenka, Hattie Morahan as Helen Sinclair and Alex Kingston as River Song.

Publisher's summary
While River Song takes Helen on an archaeological expedition like no other, the Doctor finds himself enlisted by an alien Queen to save her people.

Trapped and alone, Liv stares death in the face as she meets the enemy who's been dogging the TARDIS travellers' footsteps throughout Earth's history.

The Doomsday Chronometer has been protected for five centuries: secret cults and societies jealously guarding its mystery. But what is their real purpose? The Doctor is about to discover the truth...

Plot
Mr Whitman tells Helen that the world is ending when they are separated by a group of nuns, one of whom approaches Helen and is revealed to be River. Using her vortex manipulator, she teleports the two of them away, saying that she is a "much better driver" than the Doctor.

The Doctor is stopped by Cromwell's guards and returns to his cells in an attempt to convince them that he is not trying to escape. Nonetheless, Cromwell has him taken to Tower Green to be executed.

The Clocksmith has the Solvers take Liv to a cauldron of molten lead, but she stops him by asking for an explanation. He tells her that he came for the Syran metal to make the Doomsday Chronometer, but found before even beginning that the clock would be separated across time. He has demanded the ticket so that, once he has made the clock, he can reassemble it. He then has Liv taken to the cauldron.

Helen and River arrive in 17th century France, near Rennes-le-Château. River explains that she is wearing a psychic wimple so that the Doctor will instead see her as a woman not unlike Rita Hayworth. River explains that the castle has recently been rebuilt by the Knights Templar and that she and Helen should go and do some archaeology.

Cromwell orders his guards to leave himself alone with the Doctor before his execution and tells him that he received a visit from an emissary from the Pope who paid to speak to the Doctor. He is taken to speak to her and learns that she is a Solver called Lady Risolva.

River tells Helen that the castle was built by the Revelation Sect, who began in the mid-15th century, and leads her in through a secret passageway. In a study, they find a list of paintings of interest to the sect in which River believes there is a code and teleport away before they are found by the guards. The Clocksmith asks them what has happened. River destroys a painting and, when the alarm sounds, teleports herself and Helen to Leonardo da Vinci's studio where they collect the relevant paintings. After they leave, da Vinci runs in and rues "that woman".

To be completed.

Cast

 * The Doctor - Paul McGann
 * Liv Chenka - Nicola Walker
 * Helen Sinclair - Hattie Morahan
 * River Song - Alex Kingston
 * Thomas Cromwell - John Shrapnel
 * Solvers - Glen McCready
 * Rosalia - Emma D'Inverno
 * Octavian - Tim McMullan
 * The Clocksmith - Nicholas Woodeson
 * Risolva - Janie Dee

Continuity

 * The destruction of the planet Syra is mentioned. (AUDIO: The Sonomancer)
 * The Clocksmith watched the Doctor, Liv and Helen give the piece of the Doomsday Chronometer to Midge. (AUDIO: Absent Friends)
 * River mentions she knew another Octavian once, who was part of another church. (TV: The Time of Angels)
 * Liv recognises River as Professor Malone. (TV: The Angels Take Manhattan, AUDIO: The Sonomancer)
 * River tells Helen to have the Doctor take her to Versailles one day, but to avoid Madame de Pompadour. (TV: The Girl in the Fireplace)