Chapman’s significant stint as a child actor began with the award-winning ‘West End’ theater production ‘Billy Elliot: The Musical.’ He joined the cast in 2005 and continued playing the role for a year. He returned to the production and essayed the character ‘Michael’ in 2008 and 2009. In 2009, he was promoted to play the title character, ‘Billy.’ He continued playing the role until 2011.
He made his debut as ‘William Mulhern’ in an episode of ‘Casualty,’ titled ‘A House Divided.’ It was a British emergency medical drama series, which was also the world’s longest-running series of that genre.
After a hiatus of more than 4 years, Chapman appeared as ‘Charlie’ in an episode of the sitcom ‘Cuckoo,’ titled ‘Family Meeting.’ He also played the title character of ‘Stanley Brown’ in the series ‘The Revolting World of Stanley Brown,’ a science-based sitcom, the same year.
The year 2013 saw him in the role of ‘Richard Grey’ in ‘The White Queen,’ a period drama miniseries based on Phillippa Gregory’s historical novel series ‘The Cousins’ War.’ The same year, he also joined the cast of the highly acclaimed fantasy drama series ‘Game of Thrones,’ playing ‘Martyn Lannister,’ a trivial character who was killed in the third season.
However, in 2014, Chapman returned to ‘Game of Thrones’ as ‘King Tommen Baratheon,’ a more prominent character, in its fourth season. He reprised this role in the fifth and the sixth seasons, until the character committed suicide. This portrayal also earned him a nomination for the ‘Screen Actors Guild Award’ for ‘Outstanding Performance by an Ensemble in a Drama Series,’ along with the rest of the cast. He played ‘Chris Pollard’ in ‘Glue,’ an investigative thriller, which was appreciated by both audiences and critics.
He made his feature-film debut in 2014, playing ‘Adam Lucas’ in the psychological thriller ‘Before I Go to Sleep.’
In 2015, he appeared as ‘Harry Ward’ in an episode of ‘Ripper Street,’ a TV drama series, and as ‘Harry’ in ‘Man Up,’ a British–French romantic comedy.
In 2017, he was seen as ‘Billy Cooper’ in three episodes of ‘Will,’ an American drama series based on William Shakespeare’s life, and as Jonathan Cavendish, son of Robert Cavendish, in the biopic ‘Breathe.’
He has appeared as ‘Castor’ in ‘Into the Badlands,’ a TV series, and as ‘Danny MacCauley’ in ‘The Commuter,’ an action–thriller movie.
The year 2019 kept him busy with four films. Of the four, the two that were completed were ‘Blinded by the Light,’ a dramedy, and ‘The King,’ a historical drama. The remaining two are in different stages of production. They are ‘1917,’ a British–American war film, and ‘Here are the Young Men,’ an Irish–American drama.