Holliday Grainger is back for more detective work in the third season of the BBC's thrilling drama, The Capture. The star, 38, returns to screens on Sunday night for the fourth episode as DI Rachel Carey - a role she's recently reprised that launched her to fame in 2019.
While it's been nearly four years since the second season aired, Holliday has stayed booked and busy with roles in the BBC's JK Rowling adaptation, Strike, and the riveting period drama, The Borgias, starring Heated Rivalry actor François Arnaud and Jeremy Irons. She's become known for her on-screen roles, but off camera, the actress keeps her personal life and long-term relationship with a famous actor much more low-key.
Read on for all you need to know about Holliday's ultra-private personal life with her partner, who is also in show business.
She's dating a well-known actor
© Stefanie Keenan/Getty Images for BurberryHolliday's household is stacked with star power. The actress has been dating fellow screen star Harry Treadaway for over a decade. Harry, 41, is best known for his leading role in the thriller series Mr. Mercedes, which stars Brendan Gleeson and Holland Taylor, and the 2023 crime drama, The Chemistry of Death. He also portrayed Roddy Llewellyn in The Crown. The star even has a twin brother, Luke Treadaway, who is an actor as well and who notably starred in A Street Cat Named Bob.
Harry and Holliday have been dating since around 2015, but keep an incredibly low profile. They have made the occasional rare public appearance together on the red carpet and at London Fashion Week. Harry supported his long-term girlfriend in February 2025 at the world premiere of her film, Mickey 17, in London. The two looked loved-up as they posed for photos together at the star-studded event.
Holliday rarely talks about her relationship in public, but has given glimpses into her life with Harry here and there, including revealing to The Standard in 2015 that they collect heart-shaped stones. "It’s my boyfriend who collects them and me who keeps them," she said.
They share two kids
© Dave Benett/WireImageIn May 2021, the couple welcomed their first children, twins, while living in Devon. In an article written for The Telegraph in November 2020 while she was pregnant, Holliday opened up about being at home with her partner during the pandemic.
"Since lockdown, life has changed so much," she shared. "A lot of my jobs have been moved to 2021, so I spent most of it in Devon, where we rent a place. Having extra time together has been really lovely; the best thing was being forced to be static."
The pair have since reportedly relocated from Devon to north London, however, Holliday has never publicly confirmed the location.
Holliday previously opened up about dealing with questions around balancing work and motherhood, telling Radio Times: "People should ask, 'What's it like being a working father?' as well. These are questions that both my partner and I are dealing with because it's so new to us."
She continued: "We're both learning how to be a working mum and a working father, so those questions are actually really relevant in my own mind at the moment, because that is my world. I honestly don’t mind engaging with them because I feel like they're not engaged with enough."
