Original series (1998–2014)
With the show created, ITV assigned Chris Tarrant as its host, and set its premiere to 4 September 1998. The programme was assigned a timeslot of one hour, to provide room for three commercial breaks, with episodes produced by UK production company Celador. Originally, the show was broadcast on successive evenings for around ten days, before the network modified its broadcast schedule in autumn 2000 to air it within a primetime slot on Saturday evenings, with occasional broadcasts on Tuesday evenings.
Potential contestants needed to enter by calling a premium-rate telephone number and answering one or more questions in the style of the show. The money raised from the phone calls was used towards show prizes.
Who Wants to Be a Millionaire? proved a ratings hit, pulling in average viewing figures of up to 19 million during its broadcast in 1999 (the all-time high was on 7 March 1999, with 19.2 million viewers), though such figures often occurred when the programme was allocated to a half-hour timeslot. By September 2000, viewing figures had dropped to 11.1 million viewers, and by 2003 to an average of around 8 million viewers. Audiences continued to drop, and from 2005 to 2011 the show usually attracted between 3 and 4 million viewers.
At one point in September 1999, an episode had 60% of the TV share and caused the BBC a historic low in ratings. Over the course of his time presenting the game show, Tarrant developed a number of notable catchphrases, including "Audience, all on your keypads please. A, B, C or D. All vote now!", said when the 'Ask the Audience' lifeline is used; "Is that your final answer?", often said to confirm the contestant's answer choice and "But we don't want to give you that", when displaying the contestant's current winning cheque, to urge them on to win more money.
Since its launch, several individuals made claims over the origins of the format or elements of it, with each accusing Celador of breaching their copyrights. In three cases, the matters could not be proven by the claimants – in 2002, Mike Bull, a Southampton-based journalist, was given an out-of-court settlement when he claimed the authorship of lifelines was his work, though with a confidentiality clause attached; in 2003, Sydney resident John J. Leonard made claims in that the show's format was based on one he had made of a similar nature, but without the concept of lifelines; in 2004, Alan Melville was given an out-of-court settlement after he claimed that the opening phrase "Who wants to be a millionaire?" had been taken from a document he sent to Granada Television, concerning his idea for a game show based on the lottery.
One of the most significant claims Celador received against them was from John Bachini. In 2002, he started legal proceedings against the production company, ITV, and five individuals who had claimed they had created Who Wants to Be a Millionaire?, stating that the idea from the show was taken from several elements he had created – a board game format he conceived in 1981; a two-page TV format, known as Millionaire, made in 1987; and the telephone mechanics for a TV concept he created in 1989, BT Lottery. In his claim, Bachini stated that he submitted documents for his TV concepts to Paul Smith, from a sister company of Celador's, in March 1995 and again in January 1996, and to Claudia Rosencrantz of ITV, also in January 1996, accusing both of using roughly 90% of the format for Millionaire in the pilot for the game show, including the use of twenty questions, lifelines and safety nets, although the lifelines were conceived under different names – Bachini claimed that he never coined the phrase "phone-a-friend" that Briggs designed in his format. In response to this claim, Celador made a counter-claim that the franchise originated from the basic format idea conceived by Briggs. The defendants in the claim took Bachini to a summary hearing but lost their right to have his claim dismissed. Although Bachini won the right to go to trial, he was unable to attend the hearing due to serious illness. Celador eventually settled the matter with him out-of-court.
In March 2006, Celador began procedures to sell the format of the show and all UK episodes, as part of their first step towards the sale of their formats divisions. The purchase of both assets was made by Dutch company 2waytraffic, which were then passed on to Sony Pictures Entertainment in 2008 when it acquired 2waytraffic. As the original series progressed, variations of the format were created, and screened as special episodes, including celebrity editions, games featuring couples as contestants, and episodes themed around special events such as Mother's Day.
The Christmas celebrity special in December 2010, which was broadcast live, drew its biggest audience since 2006. To capitalise on this, and breathe new life into the show, only celebrity contestants appeared on the show from April 2011, in special live editions that coincided with holidays, events and other notable moments, such as the end of a school term. Half of the total money won in these shows went into a 'prize pot' for a viewer competition, one viewer was called live at the end of the show and asked a question to win the money. From 2012 to 2013, special episodes entitled "The People Play" were broadcast for three consecutive nights between 9 and 11 July 2012. They featured contestants from the general public with viewers at home playing along. The special was used three more times in 2013, airing across three successive weeks on Tuesday nights.
On 22 October 2013, Tarrant announced that, after fifteen years of hosting the programme, he would be leaving Who Wants to Be a Millionaire?, which consequently led ITV to decommission the programme once his contract was finished; no more specials would be filmed after this announcement, leaving only those made before it to be aired as the final episodes. After the final celebrity editions, Tarrant hosted a clip show entitled "Chris' Final Answer", which aired on 11 February 2014 (see Specials) and ended the original series.
