C Jones

Major C Jones worked at UNIT's New York Liaison Office sometime in the early 2000s. Following the deaths of Major Jones and her colleagues in the Jersey Tollgate Situation, Major A Highway, a former friend of Jones, took Jones' job at the Liaison Office, and promised to reorganise UNIT's activities in America into a single site operation, (PROSE: UNIT's New York Operation Expansion) the UNIT New York City Base, (TV: The Stolen Earth) having previously been spread across multiple divisions such as UNIT ONE and THREE. (PROSE: The Dying Days)

Major Highway expressed his sorrow of Major Jones' death, and his excitement for the future of UNIT in America, in a press briefing filed by Staff Sargeant A. Frederick. (PROSE: UNIT's New York Operation Expansion)

Behind the scenes
The Jersey Tollgate Situation is clearly intended to be a joke at the expense of the New Jersey Turnpike, an infamous toll road in New Jersey. It can then be assumed that Major Jones and her colleagues died in some sort of traffic accident.