Cullen’s personal journey mirrors his professional growth from Royal Welsh College of Music & Drama graduate to international screen regular. The table below traces the critical intersections of his public milestones and documented personal life.
| Period | Career Milestones | Documented Relationship Status |
|---|---|---|
| 2011, 2013 | Breakout in Weekend; cast as Lord Gillingham in Downton Abbey. | Began dating Tatiana Maslany after meeting on World Without End. |
| 2014, 2019 | Star of History’s Knightfall; wrote and directed Pink Wall. | Long-term domestic partnership with Maslany based in Los Angeles. |
| 2020, 2022 | Roles in Becoming Elizabeth and UK independent productions. | Amicable separation; Maslany marries Brendan Hines in 2022. |
| 2023, 2026 | Lead role in Trespasses; expansion into UK directing and theatre. | Unmarried; maintains a private dating life without public announcements. |
