To Tell the Truth is an American television panel game show, created by Bob Stewart and originally produced by Mark Goodson–Bill Todman Productions, that has aired in various forms since 1956 both on networks and in syndication.
 As of June 14, 2016, the show is one of two game shows in the United States to have aired at least one new episode in at least seven consecutive decades, the other game show being both incarnations of "The Price Is Right."
 As of the 2016 version, a total of 26 seasons of the various versions of "To Tell the Truth" have been produced, surpassing the 25 of "What's My Line?
" and the 20 of "I've Got a Secret."
A panel show or panel game is a radio or television game show in which a panel of celebrities participates.
 Participants may compete with each other, such as on "The News Quiz"; facilitate play by non-celebrity contestants, such as on "Match Game"/"Blankety Blank"; or do both, such as on "Wait Wait Don't Tell Me".
 The genre can be traced to 1938, when "Information Please" debuted on U.S. radio.
 The earliest known television panel show is "Play the Game", a charades show in 1946.
 The modern trend of comedy panel shows can find early roots with "Stop Me If You've Heard This One" in 1939 and "Can You Top This?
" in 1940.
 While panel shows were more popular in the past in the U.S., they are still very common in the United Kingdom.
It's Only a Theory is a British television panel game show, first aired on BBC Four in 2009.
 It was conceived by and starred Andy Hamilton and featured Reginald D. Hunter as a regular panelist.
 Announced by the BBC in April 2009, the eight episode series was produced by Hat Trick Productions.
Richard Dawson (born Colin Lionel Emm; 20 November 1932 – 2 June 2012) was a British-American actor and comedian, and a game show host and panelist in the United States.
 Dawson was well known for playing Corporal Peter Newkirk on "Hogan's Heroes", a regular panelist on the 1970s version of "Match Game" on CBS from 1973–78, and as the original host of the "Family Feud" game show from 1976–85, and again from 1994–95.
Tag the Gag is a very short-lived television series which aired in 1951 on NBC.
 According to IMDb, it lasted two episodes.
 It was a panel game show, a popular genre at the time.
 However, "Tag the Gag" proved unsuccessful with viewers and critics.
 It was hosted by Hal Block, best known as a regular panelist on the popular and well-received series "What's My Line?
".
 Also featured were Morey Amsterdam, Harvey Stone, Herkle Stiles, and Jean Carroll.
 The archival status of the series is not known, and it is possible (though not confirmed) that it was wiped.
Reginald Darnell Hunter (born 26 March 1969) is an American stand-up comedian based in the United Kingdom.
Dorothy Mae Kilgallen (July 3, 1913 – November 8, 1965) was an American journalist and television game show panelist.
 She started her career shortly before her 18th birthday as a reporter for the Hearst Corporation's "New York Evening Journal" after spending two semesters at the College of New Rochelle.
 In 1938, she began her newspaper column, "The Voice of Broadway", which eventually was syndicated to more than 146 papers.
 She became a regular panelist on the television game show "What's My Line?
" in 1950.
"Play to the Whistle" is a British comedy panel game television programme which premiered on ITV on 11 April 2015 and is produced by Hungry Bear Media.
 In each regular episode two teams of three members – one member being a regular captain – compete in sports knowledge rounds and physical games to earn points, the team with the most points at the end is declared the winner.
 The show is presented by Holly Willoughby and the teams are captained by Bradley Walsh and Frank Lampard; the latter is joined by Romesh Ranganathan as a regular panelist.
 Seann Walsh has been the resident scorekeeper from the first series and also became the host's assistant from the second series.
 Jimmy Bullard was the host's assistant in the first series.
 As of 4 April 2017, nineteen regular episodes and a compilation special have been aired across three series; 20 episodes in total.
The Football's On is a British television panel show broadcast on BT Sport and presented by Ian Stone with Doc Brown among others as a regular panelist.
Quite Interesting Limited is a British research company, most notable for providing the research for the British television panel game "QI" (itself an abbreviation of "Quite Interesting") and the Swedish version "Intresseklubben", as well as other "QI"–related programmes and products.
 The company founder and chairman is John Lloyd, the creator and producer of "QI", and host of the radio panel game "The Museum of Curiosity", which also uses Quite Interesting Limited for its research.
 John Mitchinson is the company's director and also works as head of research for "QI".

Question: What was the profession of the regular panelist on the British television panel game show It's Only a Theory?
Answer: stand-up comedian