2003–2008: Early roles and Robin Hood Armstrong made his professional debut in 2003, playing rookie schoolteacher Derek Meadle in ''
Quartermaine's Terms'' at
Northampton's
Royal Theatre. His performance was roundly praised by critics, who felt that he provided crucial comic relief against the story's more serious elements. He then appeared as Anthony Millington in several episodes of the
Channel 4 comedy-drama series
Teachers (2004), and again on Channel 4 in the following year's crime drama
The Ghost Squad, where he played a thrill-seeking detective assigned to expose police corruption. Armstrong's first major television role came in October 2006 when he began playing
Robin of Locksley in the
BBC One action-adventure series
Robin Hood. Though he initially faced criticism for his slight build and "boyband" good looks, his performance later drew praise, with
IGN calling it "brilliant". During filming of the
second series, Armstrong broke a
metatarsal bone in his foot during a
staged fight sequence. In August 2008, he confirmed that he would be leaving
Robin Hood the following year at the end of its third season, commenting in his statement that he was "looking for new challenges"; the BBC responded by saying that Armstrong would be "desperately missed". The show was subsequently not renewed for a fourth series.
2009–present: Film and television work In 2009, Armstrong starred in the lead role of Simon McNeal in the horror film
Book of Blood, based on a short story by
Clive Barker. Next, he guest-starred in an episode of the BBC drama series
The Street, winning praise for his "sterling work" as
TA soldier Private Nick Calshaw, who returns from
Afghanistan with life-changing injuries. That same year, he read four
CBeebies Bedtime Stories for the channel's "Bedtime Hour" segment. Between 2011 and 2012, Armstrong had roles in a succession of television crime dramas, such as
The Field of Blood, ''
Prisoners' Wives, and Hit & Miss. His portrayal of a university student-turned-Nazi impersonator in the 2014 feature film Walking with the Enemy was lauded by critics, with Paste Magazine writing, "Armstrong is [Enemy''] moral force, and he gives [the] film a forward-leaning energy; he's the character that a viewer questions whether he or she would have the guts to be. It's a performance rooted in righteousness, but Armstrong also taps into the inner conflict of a swallowed power dynamic—he locates both the lust and queasiness of playing a
Gestapo officer, and having to own that guise, and all the action it entails, at inopportune times and at a moment's notice". That same year, he played the supporting role of Skinner in the big-budget action adventure film
Edge of Tomorrow, which
Variety called a "cleverly crafted and propulsively executed sci-fi thriller". Speaking of the opportunity to work with co-star
Tom Cruise, Armstrong said at the time, "If I thought two years ago I'd be working with probably the biggest film star on the planet I would have said 'never', but it was great [...] He was really supportive and generous [and] it was an absolute privilege to work with him". In November 2013, Armstrong received a "Stars on Horizon" award at the
Fort Lauderdale International Film Festival. On the
fourth and
fifth seasons of
BBC Two's
Ripper Street (both 2016), a fictional dramatisation of the aftermath of the
Whitechapel murders, Armstrong played the recurring role of serial killer Nathaniel Croker, with
Den of Geek commenting—in their review of the fifth season's third episode—that he played the part "beautifully", adding: "It's an impressive feat for a supporting character to [take over] so completely that the main plot is barely missed". In 2018, Armstrong earned strong notices for his work in two projects: firstly, his portrayal of a
Spartan king in the
Netflix historical miniseries
Troy: Fall of a City, and then for his "convincingly exasperated" caricature of
Bob Geldof in an episode of the
Sky Arts anthology series
Urban Myths. The following year, he co-starred as Sean Meredith, a fisherman embroiled in the disappearance of his teenage twins, on the first season of the
ITV crime mystery series
The Bay. Next, he starred in
The Drowning, a four-part psychological thriller that aired on
Channel 5 in February 2021, and appeared as a grieving father who embarks on an extramarital affair in the ITV miniseries
Hollington Drive (also 2021). Armstrong's portrayal of real-life convicted sex offender
Barry Bennell in the 2022 television film
Floodlights was particularly well received by critics. Writing for
The Daily Telegraph, Benji Wilson said, "Armstrong [has] quietly been turning in performances of subtlety and power since he shot to fame [with]
Robin Hood [...] Here he was oleaginous and creepy, all simmering, smiling menace"; while Dan Einav of the
Financial Times felt that "Armstrong's ability to slip between affable mentor and depraved predator is key to his remarkably convincing performance". Speaking to
Metro shortly before the film's premiere on BBC Two, Armstrong admitted to having been reluctant to take the part: "It kind of made me feel a bit sick [but] I had a good discussion with my agent and then I decided yeah, I'm going to go for this [to] raise awareness for people who might still be suffering". In the six-part mystery thriller series
After the Flood (2024), Armstrong starred as Lee Ellison, a man whose mysterious past is unveiled when he rescues a baby from the
River Tees. His next role was that of a vengeful gangster, which the
Yorkshire Evening Post felt he played with "nerve-bulging intensity", in the four-part miniseries
Coma, which debuted on Channel 5 in March 2024. ==Filmography==