Ian J. Lygo is a British civil servant from Hemel Hempstead,(December 20, 1998). "TV quiz ace gets the boot", News of the World, p. 21. who made 75 appearances on the UK game show 100% in late 1998, with the 75th appearance occurring on 14 December of that year. Since he won £100 for each game, his total winnings were £7,500.Arnold, Harry (December 17, 1998). "Tv Quiz Chiefs Drop Mister 100 Per Cent: They alter rules after his 75th win", Daily Mirror, p. 27.
Despite the popular belief that American game show contestant Ken Jennings holds the record for longest winning streak (winning 74 games on U.S. quiz show Jeopardy!), it is Lygo who actually holds the record for longest winning streak on a game show worldwide, as he won 75 games. Lygo is the first contestant to accomplish such a streak, as Jennings' appearance on Jeopardy! did not take place until 2004.
References
Additional sources IMDB News, 17 December 1998.