He made his debut with the superhero comic Hero Killers, written by Andy Winter, which won an Eagle Award for "Favourite Black and White British Comicbook" in 2006.

[5] His small press work includes the Irish noir comic Freakshow, written by Rob Curley,[6] which featured in the small press section of Judge Dredd Megazine,[7] contributions to the anthologies Your Round Presents: Tequila,[8] The Shiznit, and the Irish language comic Rí-Rá, and Tim Skinner: Total Scumbag, again with Andy Winter.

[9] In 2008 he illustrated a graphic novel adaptation of Mary Shelley's Frankenstein, written by Jason Cobley, and in 2012 an adaptation of Sweeney Todd, written by Scottish writer Sean Michael Wilson, both for Classical Comics[10][11] He moved into American comics in 2009, drawing ten of the first twelve issues of Boom!

[12][13] In September 2010 he did his first work for Marvel, and over the next decade he drew numerous series for them, including Thunderbolts (2010–12), Fear Itself (2011), Dark Avengers (2012), Venom (2012–13), Winter Soldier (2013), Deadpool (2013), Moon Knight (2014), Groot (2015), and Return of Wolverine (2018), and writing Civil War II: Choosing Sides (2016), and Deadpool vs. Old Man Logan (2017).

[17] He collaborated with writer Warren Ellis on the creator-owned science fiction series Injection, which ran for 15 issues from Image Comics in 2015–17.