At the age of eight, Chapman was cast as "Small Boy" in
Billy Elliot the Musical, and would later be promoted to the roles of Michael and finally the titular character, becoming the second-longest running cast member in the production. During his time on
Billy Elliot, he worked alongside his friend and future
Spider-Man actor
Tom Holland, and had the opportunity to meet
Prime Minister Gordon Brown with several other young actors in the play. Soon after leaving
Billy Elliot, Chapman was cast on the
CBBC sitcom
The Revolting World of Stanley Brown in the lead role, alongside fellow future
Game of Thrones and
Blinded by the Light co-star
Nell Williams. The show lasted for one season. He made his film debut in the 2014 film
Before I Go to Sleep, alongside
Nicole Kidman and
Colin Firth. After playing the minor role of Martyn Lannister in the
third season of
Game of Thrones, he replaced Callum Wharry in the major role of
Tommen Baratheon, the young king of
Westeros for the
fourth,
fifth, and
sixth seasons of the show. With the rest of the cast, he was nominated for a
Screen Actors Guild Award. In 2018, he played the role of Castor in the
AMC series
Into the Badlands for seven episodes, followed by a supporting role in the film
Blinded by the Light. In 2019, he was cast, alongside
George MacKay, as one of the two leads in the
Sam Mendes-directed war film
1917. The film went on to receive ten
Academy Award nominations, winning three. Subsequently, he played the lead role of Matthew in the
Eoin Macken's drama
Here Are the Young Men, supported by
Finn Cole,
Anya Taylor-Joy, and
Ferdia Walsh-Peelo. == Personal life ==