Following the Sontaran invasion of Gallifrey, Lord Chancellor Borusa (TV: The Invasion of Time [+]Loading...["The Invasion of Time (TV story)"]) regenerated into a new incarnation who was Lord President by the time of the Second Omega Crisis. (TV: Arc of Infinity [+]Loading...["Arc of Infinity (TV story)"]) This regeneration was expended due to the stress upon Borusa as he took charge over Gallifrey following the Sontaran invasion. (PROSE: The Legacy of Gallifrey [+]Loading...["The Legacy of Gallifrey (short story)"])
According to another account, the Fourth Doctor's return to Gallifrey caused bad luck for Borusa such that, by the time following the Sontaran invasion, the Acting President had been forced to regenerate as a result of a falling stack of books, a missing decimal point, and an infected toenail. (PROSE: Doctor Who and the Krikkitmen [+]Loading...["Doctor Who and the Krikkitmen (novelisation)"]) However, A Brief History of Time Lords, written following the Time War, counted only three regenerations following the assassination of the 406th President: that which occurred prior to the Sontaran invasion, that which occured prior to the Second Omega Crisis, and lastly the regeneration whom would play the Game of Rassilon. (PROSE: A Brief History of Time Lords [+]Loading...["A Brief History of Time Lords (novel)"])