The Keeper during the Doctor's trial. (TV: The Ultimate Foe)
The Keeper of the Matrix, formerly known as the Coordinator of the Matrix (PROSE: The Eight Doctors) and also called the Keeper of the Record of Time, (PROSE: Mindwarp) was the Time Lord who watched over the Matrix and was in full charge of it. The Keeper kept the Key of Rassilon, the only key to the Matrix, on his person at all times. They were to keep the Matrix in good repair and make any necessary adjustments. (TV: The Ultimate Foe)
Engin served as Coordinator of the Matrix for quite some time. (TV: The Deadly Assassin) He retired whilst Flavia served as Acting President, instead sitting as an Independent on the High Council. The office was afterwards changed to "Keeper". (PROSE: The Eight Doctors)
Zon was the Keeper at the time of the Sixth Doctor's trial. He was taken over by the Valeyard. (TV: The Ultimate Foe)
Engin was once again the Keeper by the time of the Last Great Time War. (COMIC: Sky Jacks)
Councillor Volstrom consulted the Keeper during the Doom Coalition crisis. (AUDIO: Songs of Love)
Behind the scenes[]
The Keeper of the Matrix outfit used in The Ultimate Foe was bought by Andrew Beech at some point prior to 1992. That year, Beech played himself wearing the costume in the parody TV story Summer Scene.