His plays include I Caught Crabs in Walberswick, Mikey the Pikey, Food, and I Heart Peterborough, all of which have been presented on the Edinburgh Fringe.
Horwood also took part in the Old Vic New Voices 24 Hour Plays in 2006 and the celebrity version of the same event in 2009.
His play All The Little Things We Crushed was produced in 2009 at the Almeida Theatre in London directed by Simon Godwin.
[1] The cast included; Zawe Ashton, Richard Bremmer, Louise Ford, Andrew Hawley, Martina Laird and David Oakes.
He wrote the stage adaptation of The Ocean at the End of the Lane based on the novel by Neil Gaiman for the National Theatre, London which opened in December 2019.