The original British version of the show debuted on 4 September 1998, and aired on ITV with Chris Tarrant as its host until 11 February 2014. International variants have aired in around 160 countries worldwide. The show's format is a twist on the game show genre—only one contestant plays at a time (similar to some radio quizzes), and the emphasis is on suspense rather than speed. In most versions there are no time limits to answer the questions, and contestants are given the question before they must decide whether to attempt an answer.
The contestants must first play a preliminary round, called "Fastest Finger First" (or, in the U.S. version, simply "Fastest Finger"), where they are all given a question and four answers from the host and are asked to put those four answers into a particular order; in the first series of the British version and in pre-2003 episodes of the Australian version, the round instead required the contestants to answer one multiple-choice question correctly as quickly as possible. The contestant who does so correctly and in the fastest time goes on to play the main game for the maximum possible prize (often a million units of the local currency). In the event that two or more contestants are tied for the fastest time, those contestants play another question to break the tie. If no one gets the question right, that question is discarded and another question is played in the same manner. If any contestants are visually impaired, the host reads the question and four choices all at once, then repeats the choices after the music begins.
Main game contestants are asked increasingly difficult general knowledge questions by the host. Questions are multiple choice: four possible answers are given (labelled A, B, C and D), and the contestant must choose the correct one. The 'D' answer on the first question (except in the Shuffle format like in the US version) is always incorrect and humorous. Upon answering a question correctly, the contestant wins a certain amount of money. In most versions, there is no time limit to answer a question; a contestant may (and often does) take as long as they need to ponder an answer. After the first few questions, the host will ask the contestant if that is their "final answer". When a contestant says "final" in conjunction with one of the answers, it is official, and cannot be changed. The first five questions usually omit this rule, because the questions are generally so easy that requiring a final answer would significantly slow the game down; thus, there are five chances for the contestant to leave with no money if they were to provide a wrong answer before obtaining the first guaranteed amount; going for 1,000 units of currency after winning 500 units is the last point in the game at which a contestant can still leave empty-handed.
Subsequent questions are played for increasingly large sums, roughly doubling at each turn. The first few questions often have some joke answers. On episodes of the UK version aired between 1998 and 2007, the payout structure was as follows: first going from £100 to £300 in increments of £100, then from £500 to £64,000 with the pound value doubling for each new question, and finally from £125,000 to £1,000,000 with the pound value doubling for each new question.
After viewing a question, the contestant can leave the game with the money already won rather than attempting an answer. If the contestant answers a question incorrectly, then all of their winnings are lost, except that the £1,000 and £32,000 prizes are guaranteed: if a player gets a question wrong above these levels, then the prize drops to the previous guaranteed prize. Answering the £2,000 and £64,000 questions wrong does not reduce the prize money. The prizes are generally non-cumulative; that is, answering a question correctly does not result in the amount being played for being added to the amount already won, rather the amount already won is written off and replaced by a larger sum, usually twice as large. The game ends when the contestant answers a question incorrectly, decides not to answer a question, or answers all questions correctly.