He is a frequent participant on British panel shows, being a team captain on Would I Lie to You?, the host of The Unbelievable Truth on BBC Radio 4 and the former host of The Bubble and Was It Something I Said?, as well as guesting on other panel shows including QI, The Big Fat Quiz of the Year, Mock the Week, 8 Out of 10 Cats Does Countdown and Have I Got News for You.

[2] As his mother is Welsh, hailing from Swansea, and his father was born to a family that was originally Scottish,[4] he considers himself British rather than specifically English.

[9] As part of his gap year, he worked as a "general dogsbody" at Oxford University Press, in their English Language teaching division.

[13] In his first year at university, he met Robert Webb during rehearsals for a Footlights production of Cinderella in 1993, and the two men soon established a comedy partnership.

[9] Before his break into comedy, Mitchell worked as an usher at the Lyric Hammersmith theatre,[citation needed] and in the cloakroom of TFI Friday among other jobs.

"Mitchell's first project with Webb was in January 1995, a show about a nuclear apocalypse[16] entitled Innocent Millions Dead or Dying: A Wry Look at the Post-Apocalyptic Age.

[9] As a result of their performances at the Edinburgh Fringe, the duo were given the chance to write for Alexander Armstrong and Ben Miller and for series two of Big Train.

The show also featured future Academy Award and BAFTA winner Olivia Colman, who would become a regular cast member of Mitchell and Webb projects, and Martin Freeman, later of The Office fame.

[19] In 2001 the two men were commissioned for a sketch show of their own, entitled The Mitchell and Webb Situation, which ran for six episodes on the now-defunct channel Play UK.

Wessex Scene's Darren Richman said: "What the series lacked in budget, it made up for in magnificent material," and went on to call it "far superior to the vastly overrated Little Britain" and "perhaps the greatest forgotten sketch show of modern times".

TV, which released The Mitchell and Webb Situation on DVD in 2005, said that the show "gushes forth an hilarious stream of surreal and quirkily inventive sketches," as well as calling it a "cult success".

[9] Mitchell and Webb's next project came in 2003, with starring roles in the Channel 4 sitcom Peep Show, as flatmates Mark Corrigan and Jeremy Usbourne respectively.

[21] Ricky Gervais has been cited as saying: "The last thing I got genuinely excited about on British TV was Peep Show, which I thought was the best sitcom since Father Ted.

"[23] The BBC hailed Mitchell's performance in the series, stating that: "As Mark Corrigan, David reached out to all those middle-aged men in a twentysomething's body, who believe drugs are boring and systems are necessary if society is to function at all.

[24] In 2009, Mitchell won the British Academy Television Award for Best Comedy Performance for his work on Peep Show, after having lost in the same category the year before.

[36] The tour was criticised as just "a succession of largely unrelated scenes" by The Guardian's Brian Logan, who gave it a rating of two stars.

[33] Later in 2007, the pair recorded a pilot BBC Radio 2 sitcom entitled Daydream Believers, in which Mitchell played Ray, a science-fiction writer.

[34] One journalist called the adverts "worse than not funny", and accused Mitchell and Webb of "an act of grave betrayal" for taking corporate work.

[52] In an interview with The Telegraph, Robert Webb responded to the duo's critics, stating that "when someone asks, 'Do you want to do some funny ads for not many days in the year and be paid more than you would be for an entire series of Peep Show?'

[63] He provided the voiceover for a £1 million government advert for FRANK, warning of the dangers of cocaine, as "Pablo the Drug Mule Dog";[64] and also for the Driving Standards Agency's "The Highway Code".

[66] He also took part in Channel 4's Comedy Gala, a benefit show held in aid of Great Ormond Street Children's Hospital at the O2 Arena.

[82] Mitchell made his stage debut in Ben Elton's The Upstart Crow which premiered in London in February 2020 at the Gielgud Theatre.

[89][90] He hosted the second week of Channel 4's FAQ U, and appeared as himself in an episode of Rob Brydon's Annually Retentive, a panel show parody.

In a 2007 interview with Digital Spy, Mitchell stated that he enjoyed panel shows, as they are "a game worth playing".

[3] He then further explained his appreciation of the panel format by challenging criticism from Fast Show co-creator Charlie Higson, who stated in September 2013 that panel comedies were overtaking television programming at the expense of sketch shows and sitcoms: There was a quote from Catherine Zeta-Jones about playing golf with her husband Michael Douglas.

[86]The Radio Times named him "The Best Comedy Panel Show Guest" in the world, stating that "he's incredibly, disgustingly witty" and "even starting to make Paul Merton look slow on the uptake".

In reference to his ubiquitous presence in broadcast and print media, The Guardian's writer called him "the go-to funnyman of the moment".

[9] Additionally, following the death of British actor Richard Briers in February 2013, Mitchell revealed that whenever he has acted he "always hoped to be something like him".

"[108] In his 2007 interview on Parkinson, he said that if he could go back in time to do one thing, he would choose to attend the construction of Stonehenge to ask them "why they were bothering".

[118] Mitchell, who has Scottish ancestry, was one of 200 public figures who signed an open letter to The Guardian in August 2014 expressing their hope that Scotland would vote to remain part of the United Kingdom in September's referendum on that issue.