Flavia

Chancellor Flavia first encountered the Doctor when Borusa summoned the Doctor's selves to the Death Zone.

Following Borusa's entombment in the Dark Tower the High Council granted Flavia the power to make the Doctor President of the High Council.

He used his emergency powers to place Flavia in charge until he returned. She later assumed the role of President.

Challenge of Presidency
Following her return to Gallifrey from E-space Romana challenged Flavia for the role of President and won.

Behind the scenes
According to various commentaries on the Series 1 & 2 DVDs of the BBC Wales Doctor Who, Russell T. Davies refers to the soft female voice in the music as 'Chancellor Flavia'.