Thaddea Graham

Thaddea Graham (born 29 March 1997) is a Northern Irish actress. On television, she is known for her roles in the Sky One series Curfew, the Netflix series The Letter for the King (2020), The Irregulars (2021) and Sex Education (2023), the BBC series Us (2020), Doctor Who (2021) and Wreck (2022), and the Apple TV+ series Bad Sisters (2024) and Margo's Got Money Troubles (2026). Her films include After the Hunt (2025).

Graham appeared on the 2023 Screen International Rising Stars Ireland list.

Early life and education Graham was adopted from an orphanage in Changsha, China at one year old and was raised in County Down. She was one of the first international adoptees in Northern Ireland. Graham attended Killinchy Primary School in Killinchy and later Bloomfield Collegiate School in Ballyhackamore. She trained with Arts Educational School in London, graduating with a Bachelor of Arts in Acting in 2018.

Career Graham made her television debut with a recurring role in season 3 of The Sparticle Mystery. In December 2018, she landed her first major role as Iona in the 2020 Netflix fantasy series The Letter for the King, an adaptation of the classic Dutch book by Tonke Dragt. The following December, she was cast as Bea in the 2021 Sherlock Holmes spinoff The Irregulars, also on Netflix. In the meantime, she played Hanmei Collins in the Sky One action series Curfew, and Kat in the BBC One comedy-drama miniseries Us. She joined the cast of Doctor Who for its thirteenth series (known as Doctor Who: Flux) as Bel, making her debut in "Chapter Three: Once, Upon Time".

In 2022, Graham was in the main cast of the Virgin Media One and ITV crime drama Redemption as Siobhán Wilson and began starring as Vivian Lim opposite Oscar Kennedy and Jack Rowan in the BBC Three horror comedy Wreck. She joined the cast of the Netflix comedy-drama Sex Education for its fourth season playing the character "O".

In 2024, Graham was announced as part of the cast of Margo's Got Money Troubles created by David E. Kelley.

Filmography

Film Year Title Role Notes 2014 Painkiller Short film 2021 VHS Lea Short film 2022 Ballywalter Frances 2025 Jay Kelly Meg 2025 After the Hunt Katie 2026 TBA Post-production TBA TBA Filming

Television Year Title Role Notes 2015 The Sparticle Mystery Lucie 3 episodes Dani's Castle Atka Episode: "Groundbog Day" 2019 Curfew Hanmei Collins Main cast 2020 The Letter for the King Iona Main cast Us Kat Miniseries, main cast 2021 The Irregulars Bea Main cast Doctor Who Bel 3 episodes 2022 Redemption Siobhán Wilson Miniseries, main cast 2022–2024 Wreck Vivian Lim Main cast 2023 Sex Education Sarah 'O' Owens Main cast (series 4) 2024 DNA Journey Herself – Narrator 3 episodes Bad Sisters DI Una Houlihan Main cast (series 2) 2026 Margo's Got Money Troubles Susie Miniseries

Video games Year Title Role Notes 2022 Sifu Fighter (voice) 2023 Dead Island 2 Jessie (voice)

Stage Year Title Role Notes 2016 London Stories Made by Migrants Battersea Arts Centre

Awards and nominations

Year Award Category Work Result 2025 Edinburgh International Television Festival Breakthrough Performance