Countdown Marathon is the name given to two charity games played by Series 65 semi-finalist Mark Deeks, the first against Series 61 semi-finalist Innis Carson and the second against Series 69 and Series 78 contestant Zarte Siempre, on both occasions supporting an equally-long stand-up comedy act by Mark Watson.
The first game was played in 2013, with Carson winning against Deeks on a crucial conundrum, and lasted 450 rounds exactly, following a pattern of 4:1 letters:numbers, and culminating in one conundrum. The format was slightly changed when a sequel was played in 2019, playing 36 15 round games of Countdown. The result was slightly less close, with Deeks beating Siempre by 29 points.
Both games featured Rachel Riley taking a turn as host.
|#||Date||Type||Contestant 1||Score||Contestant 2||Guest||Lex||Max|
|Countdown Marathon 1||28/02/2013||X||Mark Deeks||3116 – 3128||Innis Carson||Rachel Riley||Zarte Siempre||3550|
|Countdown Marathon 2||27/02/2019||X||Mark Deeks||3558 – 3529||Zarte Siempre||Rachel Riley||Innis Carson||4338|