Born in Owestry, an English border town near Wales, Armstrong attended the University of Manchester in the early 1990s, where he met Sam Bain in a creative writing course. After graduation, the pair kept in contact by writing humorous letters to each other, which convinced them to try their hand at writing for television. Armstrong had been released from his job as a researcher for Labour MP Doug Henderson, and with Bain, he contributed sketches to the popular comedy series "Smack the Pony" (Channel 4, 1999-2003) and several children's series, including the long running "My Parents are Aliens" (ITV, 1999-2006). The pair also wrote a pilot for a proposed series called "Bread Heads," about hapless would-be entrepreneurs, which brought them to the attention of comedians David Mitchell and Robert Webb. The duo commissioned Armstrong and Bain to create a series for them, which became "Peep Show." The sitcom, about the misadventures of two male friends from South London and their circle of girlfriends, neighbors and co-workers, was immediately distinguished by its semi-documentary style, which viewed the lives of the protagonists entirely from their point of view, with their thoughts heard in voice-over. Though a critical favorite and recipient of several UK television awards, "Peep Show" was never a ratings success throughout its nine seasons, which concluded in 2015, but it firmly established Armstrong and Bain as fresh new voices in British television comedy. While overseeing "Peep Show," Armstrong and Bain worked on a variety of other projects for television, radio and film. With Mitchell and Webb, they wrote the theatrical feature "Magicians" (2007) and for the BBC Radio 4 series "That Mitchell and Webb Sound," a sketch comedy program that later became a television show, "That Mitchell and Webb Look" (BBC Two, 2006-2010). The pair also created the short-lived comedy series "The Old Guys" (BBC One, 2009-2010), about a pair of elderly housemates, while Armstrong worked without Bain on the critically acclaimed, BAFTA-winning political satire "The Thick of It" from writer-producer Armando Ianucci. He continued to collaborate with Ianucci on two projects spun off from "Thick": the feature film "In the Loop" (2009), which received an Oscar nomination for Best Adapted Screenplay, and the American comedy series "Veep" (HBO, 2012-). During this period, Armstrong also gave voice to his political interests about the 2010 general election by penning a column for The Guardian, and wrote a screenplay for "Murdoch," a comedy about multimillionaire Rupert Murdoch haggling with his family over control of his company, which went unproduced. In 2011, Armstrong reteamed with Bain to create "Fresh Meat," a sitcom about six medical students sharing off-campus housing at a fictitious Manchester University. As with "Peep Show," the new series was a critical success, reaping wins from the British Comedy Awards and Royal Television Society Awards, and a proposed movie spin-off. Their next small screen effort, the soap opera satire "Bad Sugar" (Channel 4, 2012), was commissioned for series but then cancelled by the network over scheduling issues regarding the main cast, which included their longtime collaborator, actress Olivia Colman. Undaunted, Armstrong and Bain teamed with director Danny Boyle and Robert Jones to create "Babylon," a comedy-drama about the lives of London police officers and the public relations office that supports them. During this period, Armstrong also wrote scripts for or was attached to a number of high-profile film projects, including a biopic about Republican strategist Lee Atwater and an adaptation of Richard DiLello's The Longest Cocktail Party, about the history of Apple Records.