Blackwell started writing TV comedy in 1999 on shows such as Have I Got News For You, The Kumars at No. 42, Alastair McGowan's Big Impression and The Armstrong and Miller Show, for which he created the duo's street-talking RAF pilot characters.
He first worked with Armando Iannucci in 2003 on the topical Channel 4 show Gash. He went on to write on all four series of Iannucci's political sitcom The Thick of It and co-wrote its spin-off film In The Loop, which was nominated for an Oscar for Best Adapted Screenplay.
Other work with Iannucci includes 2004: The Stupid Version and Time Trumpet.
Blackwell wrote for Chris Morris's 2010 black comedy film Four Lions, alongside Jesse Armstrong and Sam Bain. He had previously collaborated with them on the Channel 4 sitcom Peep Show and BBC One's The Old Guys.
In 2016, Blackwell created the sitcom Back starring David Mitchell and Robert Webb. It premiered on Channel 4 on the 6th of September, 2017.
