Was originally broadcast on British regional TV channel Yorkshire Television, at 6.30pm following the local news programme Calendar (1968), and was originally called "Calendar Countdown". Richard Whiteley was (and had been for years) a presenter on "Calendar" from 1968 until 1995. "Countdown" shortly thereafter moved to Channel 4 upon that channel's launch. Originally, Carol Vorderman (then a newcomer) was only there to perform the numbers rounds of the game - the letters rounds were presented in the early series by another hostess.
In May 2005, Richard Whiteley caught pneumonia, and his position as host was to be temporarily filled by a series of guest presenters during the recording of Series 54. He later died in June, and after auditions for a new host the show returned in October hosted by Desmond Lynam. The guest-presented episodes were never aired, and a new Series 54 was recorded instead. Others who auditioned included Richard Digance and Noel Edmonds; Paul Merton was also rumored to have been under consideration.
25 themed specials were recorded between 2002 and 2003, of which only 23 were broadcast (in 2003-2005), and which each featured two previous contestants. The other two specials were never broadcast because they were presented by Richard Whiteley, and as the specials were only intended to be broadcast infrequently (some were scheduled, others shown in place of cricket matches), Whiteley died in 2005 before the last two could be shown and they have not been broadcast since. One was based around the theme of a replayed final, and the other was based around the theme of old Countdownians.
By the time Carol Vorderman left the show in December 2008, she has been in more than 4700 episodes, she put more than 320,000 letters on the letters board, tackled more than 11,200 numbers games and heard the Countdown music more than 57,000 times.