In 2008, Lewis, Jonathan Sayer, and Henry Shields co-founded Mischief Theatre while they were studying a drama foundation course at the London Academy of Music and Dramatic Art.

[1] In 2012, Lewis co-wrote with Sayer and Shields The Play That Goes Wrong,[2] which premiered later that year at The Old Red Lion, Islington.

[5] In 2013, another Lewis, Sayer and Shields production, Peter Pan Goes Wrong, premiered at The Pleasance Theatre.

[14] In 2020, Lewis launched The Mystery Agency, an escape-room style puzzle game, on Kickstarter.

[20] In 2022, he started playing the Riddlemaster in Riddiculous, an ITV daytime game show hosted by Ranvir Singh.