Mary Elson was the niece of Reverend Matthew Townsend. Her parents died in a car crash. In 1951, she accompanied her uncle to the Cardington airbase, where he became involved with the Dionysus Project. After its creator Professor Stone activated the Dionysus machine, Townsend overloaded it, tore a rip in the fabric of reality and saw the Divergence. Shortly thereafter, Mary was killed by a bomb planted by the Cuban spy Miss Foster, as were her uncle, Stone, Captain Neil McDonnell and Foster herself.
While dealing with the aftermath of the explosion of anti-time, the TARDIS created a series of holographic projections, taken partly from reality and partly from the memories of the Eighth Doctor, Charley Pollard and the TARDIS itself. One such projection was the event at Cardington, looking for information on the Divergence. Inside this projection, it placed Charley in the role of a ministry driver and itself in the role the Minister for Defence. The projection of Mary was created using the image of the Fifth Doctor's companion Erimem. (AUDIO: Zagreus)