Season 23 Season 23 of " Doctor Who " ran between 6 September 1986 and 6 December 1986 . It starred Colin Baker as the Sixth Doctor . Though produced as four separate serials from a practical standpoint , it aired as a single , connected serial entitled The Trial of a Time Lord . With this season the BBC returned " Doctor Who " to an autumn season start for the first time since Season 18 ; this scheduling would remain for the rest of the original series ' run . Overview . This season had a unique format , never again repeated in the show . " Doctor Who " had returned to production after a near - cancellation and an eighteen month production hiatus . For the first time , a season consisted of a single story , " The Trial of a Time Lord " , although this was made up of four serials from a production perspective : each serial was written by a different person ( save for " The Mysterious Planet " and the first part of " The Ultimate Foe " , both of which were written by Robert Holmes ) and featured a different story presented as evidence , excluding the final two episodes which concluded the ongoing story of the trial ; the trial storyline itself acted as a to bracket the first three serials . As a result , whether " The Trial of a Time Lord " should be considered one story or four has been intensely debated . This single - story format , sometimes referred to as a " miniseries " , would later be utilised for the third and fourth series of " Torchwood " . In an interview in " Doctor Who Magazine " 448 , " Timelash " author Glen McCoy said that he came up with the idea of the Doctor being put on trial . The experiment of forty - five - minute episodes having been deemed a failure , the BBC reverted the series to twenty - five - minute episodes , but kept the episode count at fourteen , effectively halving the number of episodes in a season . The last episode , however , ran thirty minutes . This format lasted for the remainder of the classic series . This was the final season to feature Colin Baker as the Sixth Doctor ; he was fired following its conclusion . He did not return to play the Doctor for the regeneration scene in " Time and the Rani " , the first story of the following season . It was the last season to use the " neon tubing " logo introduced in 1980 . A new arrangement of the " Doctor Who " theme by Dominic Glynn was introduced this season , but was only used for these fourteen episodes , before being replaced by another new arrangement . The final serial of Season 23 turned out to be veteran writer Robert Holmes ' s last contribution to the series , falling gravely ill and passing away before he could finish the script . It was then passed to script editor Eric Saward , who tried to finish the script but got into an argument with producer John Nathan - Turner over its ending . Eventually , Saward gave up and quit working on " Doctor Who " altogether , withdrawing his contributions to Holmes ' s script as he left . The script was then passed along to Pip and Jane Baker , who completed it as they saw fit . Aborted Season 23 . Prior to " Doctor Who " being placed on hiatus after Season 22 , a slate of serials of standard length was planned , and scripts were written for several . The decision to recast Season 23 as a single interconnected arc resulted in production of these stories being cancelled . Three of the stories were subsequently adapted as Target Books novelisations : " The Nightmare Fair " ( which would have seen the return of the Celestial Toymaker ) , " Mission to Magnus " ( featuring Sil and the Ice Warrior s ; Sil ultimately appeared in the " Mindwarp " segment of the " Trial of A Time Lord " ) , and " The Ultimate Evil " . An unofficial audio adaptation of " The Nightmare Fair " was also produced for charity in 2003 . Beginning in late 2009 , Big Finish Productions launched a series of audio dramas covering scripts that had never made it to production , titled " The Lost Stories " . The first season featured adaptations of " The Nightmare Fair " , " Mission to Magnus " , and other story lines planned for the aborted Season 23 . Adaptations and merchandising . Home media . DVD . All serials of " The Trial of a Time Lord " were released in a complete box set on 29 September 2008 in region 2 , on 7 October 2008 in Region 1 , and on 5 January 2009 in Region 4 . Stories set during this season . During " The Ultimate Foe " : Before " Terror of the Vervoids " from Mel ' s perspective : Between " Terror of the Vervoids " and " The Ultimate Foe " from Mel ' s perspective :