He was spotted while performing in a festival by talent scout Patrick Duncan, who was working for Aisling Walsh, the director of Song for a Raggy Boy.
After completing his law degree, he returned to Northern Ireland, and worked at a building site while continuing to audition.
[2] Simpson's first film appearance was as Gerard Peters 458 in Song for a Raggy Boy (2003), a story about an Irish reform school.
[3] In 2012 he appeared in the docudrama Saving The Titanic as electrician Albert Ervine, the youngest member of the engineering crew, which reunited him with Song for a Raggy Boy co-star Chris Newman.
[5] He re-teamed with director Abner Pastoll for the crime thriller A Good Woman Is Hard to Find starring Sarah Bolger, which was released in 2019.