The Last Line of Defence (audio story)

 was the third and final story in the audio anthology Visitants, produced by Big Finish Productions. It was written by Robert Valentine and featured Angela Bruce as Brigadier Bambera, Alex Jordan as Sergeant Savarin and Yemishi Oyinloye as Dr Louise Rix and Liz Sutherland-Lim as Dame Lydia Kingsley.

Publisher's summary
With the civil war in Valge Maja threatening to spark an even greater conflict, Bambera is put in charge of security at a secret Millennium Eve peace conference to settle the matter. But as all of Earth's leaders gather to debate the future of humanity, dark forces have conspired to ensure that this meeting will usher in a terrifying New World Order - and with the clock ticking, who can possibly stand in their way?

Plot
As Vabados City in Valge Maja is besieged and the civil war looks set to cause a third world war, Fidelia Esperanza, President of the Unified Nations Security Council, calls for a conference to be held on neutral ground to bring an end to the bloodshed. The Omniarch of the Zeta Hydri decides that now is the time for her invasion of Earth.

Dame Lydia puts Bambera in charge of security for the conference at St James's Palace instead of the Queen's Colonel Birch, causing some tension, and also brings in UNIT Internal Security. Rix liaises with NASA and various other space agencies and telecommunications companies to resolve the issue of half of the world's satellites being non-operational and, when they all become operational again, she tells Savarin that something might have entered Earth's orbit during the blackout. She is correct and human allies of the Zeta-Hydri send them the location of the secret conference.

During the conference, the Hoplite Frequency is initiated, leaving the delegates unconscious, and Bambera and Savarin put in cancelling earpieces to combat it. The Zeta Hydri arrive in their spacecraft and attack Bambera, who runs and asks Rix to find out how the Zeta Hydri got a hold of the frequency. She is captured and taken before the Omniarch and learns that Dame Lydia has been working with her; Dame Lydia commands Bambera to call for a surrender, but she refuses and Esperanza is executed.

Birch, an MI6 agent, takes Rix to the Vauxhall Building and explains that he has been feeding Bambera information in the hopes that she would help the cause, being unsure if he could trust UNIT. He has learnt from Prisoner 1, a Zeta Hydran, of the Omniarch's plans who reveals that his kind can stun people using sound projection. Rix records the data and uses it against the prisoner, accidentally turning him into soup. Birch congratulates her and they head to the palace through a World War II secret passageway in the basement of a wine merchant's on St James's Street and bump into Savarin. They switch off the Hoplite Frequency and transmit the sound projection, but Birch is mortally wounded.

Bambera escapes her guard and is reunited with Savarin and Rix. The Zeta Hydri suffer because of the sound projection and Lydia tries to escape in a helicopter, but Birch sabotages it and the helicopter crashes, after which Bambera arrests her.

The Valge Majan rebels agree to a ceasefire to begin discussing terms of peace and UNIT cover up the Zeta Hydri invasion by claiming that the spacecraft was an untethered balloon from a film set. Bambera informs Savarin and Rix that UNIT Central Control have deemed UNIT-UK's headquarters and undefendable and that a new base will be built at the Tower of London. The trio celebrate the ushering in of the new millennium with champagne.

Cast

 * Brigadier Winifred Bambera - Angela Bruce
 * Sergeant Jean-Paul Savarin - Alex Jordan
 * Dr Louise Rix - Yemisi Oyinloye
 * Dame Lydia Kingsley - Liz Sutherland-Lim
 * Colonel Birch - Ian Abeysekera
 * The Omniarch - Lesley Ewen
 * President Esperanza - Chandrika Chevli
 * UNIT Trooper - Timothy Blore
 * Delegate - David Menkin
 * Zeta Hydran 1 - Jason Forbes
 * Zeta Hydran 2 - Nathaniel Curtis

Worldbuilding

 * Savarin mentions the Millennium Bug.
 * UNIT Internal Security assist with the conference security.
 * It was believed by the public that the conference would be held in Brasília or Geneva.
 * Samantha works at Jodrell Bank Observatory.
 * MI6 are based at the Vauxhall Building.
 * Zeta Hydra IV is about 285 light-years away.
 * MI6 and the SOE used a secret passageway between a wine merchant's on St James's Street and St James's Palace. According to legend, it was used by James II.

Continuity

 * The Hoplite Frequency is used. (AUDIO: The Frequency)
 * Rix mentions Helena McNamara's death. (AUDIO: Dark Side of the Moon)
 * Savarin suggests Rix tries "reversing the polarity". (TV: The Dæmons et al)
 * Bambera informs her team, Unit will be moving into the Tower of London in the new year. (TV: The Christmas Invasion et al)