During this time he wrote for the political satire series The Thick of It (2005–2009) and co-wrote In the Loop (2009), the latter of which earned him a nomination for the Academy Award for Best Adapted Screenplay.

[9] To date, Armstrong and Bain have written two films together – the 2007 comedy Magicians, and, alongside Chris Morris, the 2010 terrorism satire Four Lions.

In 2012 both Armstrong and Bain were featured on the TV industry journal Broadcast's 'Hot 100' list, highlighting the most successful people in UK television.

[10] In 2012, Armstrong and Bain wrote the Channel 4 comedy pilot Bad Sugar, a spoof of Dynasty-style soap operas, which stars Olivia Colman, Julia Davis and Sharon Horgan, all of whom also co-conceived the show.

Alongside Armando Iannucci, Simon Blackwell and Tony Roche, Armstrong wrote for the first three series[12] of the BAFTA-winning BBC Four comedy The Thick of It, and its 2009 film spin-off In the Loop.

Alongside The Thick of It's writing team, Armstrong wrote one episode of the first season of HBO comedy series Veep, set in the office of the American vice-president.

[15] In the wake of the 2011 phone hacking scandal involving newspapers owned by Murdoch it was rumoured[16][17] that the script was being developed by Channel 4, but Armstrong dismissed these claims.

[18] In 2010 it was reported that Armstrong was developing a biopic of the Republican Party strategist Lee Atwater, with Chris Henchy and Adam McKay.

[citation needed] Armstrong wrote one episode of Charlie Brooker's anthology series Black Mirror, entitled "The Entire History of You".