Muriel Frost

Captain (later Colonel) Muriel Frost worked for UNIT. On a number of occasions, she worked with the Doctor's seventh incarnation.

Biography
In 1980, as a UNIT Captain, she met with Scalini at Pompeii, where the Professor had discovered a police box buried in the ruins. (AUDIO: The Fires of Vulcan)

Working undercover, Frost investigated Stranks, the owner of a night club suspected of selling a potent street drug called Mandrake. At the same time, the Seventh Doctor and Ace had been drawn to Earth by the alien energy structure known as the Mandragora Helix. It had contacted Stranks and used him to produce Mandrake, which sapped the will of its users and made them susceptible to the Helix's influence. The Doctor and Ace worked with Frost to thwart the Helix again. During the course of this venture, she received a field promotion to Colonel. (COMIC: The Mark of Mandragora)

Investigating the crash of a World War II fighter plane with the Seventh Doctor, Frost entered the mind of the dead pilot and discovered that the crash had been the result of a collision with a Q'Dhite ship which a local clerk, Alex Evening had turned into his own private, miniature world. The Doctor and Frost entered Evening's world with UNIT troops. They destroyed the illusion and sent Evening into an irreversible coma. (COMIC: Evening's Empire)

After the London UFO crash on 6 March 2006 (TV: Aliens of London) or 28 June 2006, (PROSE: Operation London) Frost and her Geneva EVA team (PROSE: Number Ten) were summoned to 10 Downing Street (TV: Aliens of London) from Geneva. (PROSE: Operation London) She was summoned to be an advisor on extraterrestrial activity, coming dressed in her US Army Major uniform. However, she was killed by the Slitheen family who had infiltrated Earth's government. (TV: Aliens of London) Major Jenny Maguire shortly after officially announced her and her team's death on an operations board to other UNIT officers. She had to inform the families of the deceased, and later saw the coffins off an air strip. (PROSE: Number Ten)

Other timelines
In a world where humans had a working relationship with the Silurians, Frost was a member of URIC, that world's equivalent to UNIT. (COMIC: Final Genesis)

Personality
Fiery in both hair colour and temperament, Frost was a no-nonsense and efficient UNIT operative who had problems maintaining personal relationships. (AUDIO: The Fires of Vulcan) Major Jenny Highway, who was familiar with Frost, joked that "[she would] like to see anyone face her down", referencing her temperament. (PROSE: Operation London)

Behind the scenes

 * In early drafts of 2005's Aliens of London, the Ninth Doctor specifically named one of the uniformed characters as Muriel Frost. (REF: DWMSE 11) In the final cut of the episode, the nametag "FROST" is still visible on her uniform.
 * PROSE: Operation London and Number Ten, two short stories that were released to coincide with Aliens of London and World War Three, explicitly references Frost by her surname.
 * The 2005 Classified! A Confidential 3-D Dossier activity book included a closing note from General Muriel Frost.