Type 50

Type 50 was a type of TARDIS used by Time Lords. It was much more advanced than the Type 40s. The First Doctor owned a Type 50 TARDIS before leaving Gallifrey in a stolen Type 40 TARDIS. (AUDIO: Prisoners of Fate) Maris heard rumours that some Type 50s could take on human form. (PROSE: Celestial Intervention — A Gallifreyan Noir)