The Reaffirmation Ceremony was a ritual conducted by the Time Lords every one-hundred-and-fifty years in which the Lord President, Vice President, Chancellors and Castellan would renew their allegiance to Gallifrey through Vows of Reaffirmation. The Dromeian Archibaptrix was involved in this ceremony.
President Romana delayed the preparation of her speech at the Reaffirmation Ceremony in order to greet the Eighth Doctor. (PROSE: The Ancestor Cell)