Theo Stevenson was born in 1998 in Essex, England, he played Horrid Henry in the 2011 film Horrid Henry: The Movie (Trailer) which opened July 29 in the UK. Stevenson who was born in Essex, England, UK shares the screen with an all-star cast.

The first ever British kids' movie to be filmed in 3D, 'Horrid Henry: The Movie' stars Anjelica Huston as Henry's terrifying teacher Miss Battle-Axe, alongside Rebecca Front as Henry's headmistress Ms. Oddbod, Richard E. Grant as a rival headmaster, and Parminder Nagra as Miss Lovely.

The film sees Horrid Henry, Lord High Majesty of the Purple Hand Gang, waging his ever constant battle against the tyranny of adults, only this time it seems the adults really are out to get him!

Theo also appeared in the films Reuniting the Rubins (2010) as Jake Rubin, In Bruges (2008) and Fred Claus (2007) as Young Nick - 6 Yrs Old. Theo also played Ethan in the Ben Gregor film, All Stars (2013). He will play jake in the feature "Butterfly Kisses" (2017).

On television, he appeared in an episode of the series "Little Crackers" in 2010. He also played Craig on the series "Millie Inbetween" (2014) and playing Toby Hawkins on "Humans" (2015)

Theo's theatrical credits include Young Vic productions of The Human Comedy and Member of the Wedding, and the national Theatre's Dido, Queen of Carthage directed by James Macdonald.