He first appeared on Countdown on 16 July 1990, beating his opponent Richard Hooke 42 – 37. He beat a further seven opponents to become the only octochamp of the series, and duly returned for the final rounds as #1 seed. (In Coombs' seventh game, he scored 72 points, which was the highest score of the series, even including the 14 round grand final.) After inflicting a heavy defeat on Denys Hollis in the quarter-finals and beating Maurice Binks in the semis, he faced Liz Barber in the final. Trailing by one point going into the conundrum, Coombs buzzed in on 18 seconds and looked to have won it, but his answer was incorrect. Barber also answering the conundrum incorrectly later on proved to be academic - Coombs had lost the game, and the series, by a single point.
Oddly, Coombs did not return for Championship of Champions V at the start of the next series, instead returning in 1993 for Championship of Champions VI, where he was beaten in the first round by Fiona Willis.
|#||Date||Type||Contestant 1||Score||Contestant 2||Presenters||Guest||Lex||Max|
|1013||16/07/1990||P||Derek Coombs||42 - 37||Richard Hooke||Richard Whiteley||Carol Vorderman||Gyles Brandreth||Della Thompson||84|
|1014||17/07/1990||P||Derek Coombs||56 - 15||Pat Daines||Richard Whiteley||Carol Vorderman||Gyles Brandreth||Della Thompson||69|
|1015||18/07/1990||P||Derek Coombs||57 - 30||Neil Kendall||Richard Whiteley||Carol Vorderman||Gyles Brandreth||Della Thompson||68|
|1016||19/07/1990||P||Neil Rich||49 - 58||Derek Coombs||Richard Whiteley||Carol Vorderman||Eve Pollard||Simon Mason||71|
|1017||20/07/1990||P||Duncan Dale-Emberton||33 - 63||Derek Coombs||Richard Whiteley||Carol Vorderman||Eve Pollard||Simon Mason||74|
|1018||23/07/1990||P||Mollie Haigh||18 - 68||Derek Coombs||Richard Whiteley||Carol Vorderman||Eve Pollard||Simon Mason||76|
|1019||24/07/1990||P||Colin Blumen||44 - 72||Derek Coombs||Richard Whiteley||Carol Vorderman||Eve Pollard||Simon Mason||73|
|1020||25/07/1990||P||Kevin Roberts||44 - 46||Derek Coombs||Richard Whiteley||Carol Vorderman||Eve Pollard||Simon Mason||81|
|1061||20/09/1990||QF||Derek Coombs||69 - 10||Denys Hollis||Richard Whiteley||Carol Vorderman||Simon Williams||Simon Mason||73|
|1065||26/09/1990||SF||Derek Coombs||51 - 34||Maurice Binks||Richard Whiteley||Carol Vorderman||Tim Rice||Simon Mason||67|
|1067||28/09/1990||GF||Derek Coombs||66 - 67||Liz Barber||Richard Whiteley||Carol Vorderman||Tim Rice, Gyles Brandreth||Simon Mason||124|
|1329||5/01/1993||CQF||Derek Coombs||54 - 64||Fiona Willis||Richard Whiteley||Carol Vorderman||Richard Stilgoe||Susie Dent||83|
|1857||11/10/1996||aQF||John Clarke||58 - 52||Derek Coombs||Richard Whiteley||Carol Vorderman||Nigel Rees||Susie Dent||72|