In 2008, Daniels made his Broadway début in a revival of Les Liaisons Dangereuses, for which he was nominated for the Tony Award for Best Actor in a Play.

Daniels has also appeared on popular television series including Cutting It (2002–04), The Virgin Queen (2005), Law & Order: UK (2009–11), The Paradise (2013), House of Cards (2013–14), and The Exorcist (2016–17).

On 1 April 2018 he appeared in the NBC live televised concert rendition of Andrew Lloyd Webber and Tim Rice's rock opera Jesus Christ Superstar as Pontius Pilate.

[6][9] One of Daniels' earliest roles was as Justin Hayward, the lead singer of the Moody Blues, as a teenager in two of the band's music videos, "Your Wildest Dreams" (1986) and "I Know You're Out There Somewhere" (1988).

[10] In 2008 he appeared in Lark Rise to Candleford, a BBC production based on three semi-autobiographical novels about the English countryside written by Flora Thompson.

Daniels has also played a number of real-life characters, such as German State Secretary Dr. Josef Bühler in Conspiracy, a 2001 dramatisation of the Wannsee Conference at which the Final Solution was endorsed.

In an independent film directed by Lavinia Currier titled Passion in the Desert (1997), Daniels played a French soldier named Augustin Robert.

Other theatre credits include Waiting for Godot (1994) and 900 Oneonta (1994), which earned him a nomination for Best Actor at the Evening Standard Awards.

[6] He also acted in Martin Yesterday (1998), for which he was nominated as Best Actor in the Manchester Evening News Theatre Awards,[6] Naked (1998), Tales From Hollywood (2001), Three Sisters (2003), Iphigenia at Aulis (2004), The God of Hell (2005), and The Wild Duck (2005–2006).

He was first nominated for the latter award earlier in his career, in 1991, for his performance as murderer Richard Loeb in the play Never the Sinner at the Playhouse Theatre.

[19] In 2008, Daniels fulfilled a lifetime ambition[14][21] when he made his Broadway début, headlining as the Vicomte de Valmont in a revival of Les Liaisons Dangereuses.

[24] Daniels played a recurring role as prominent photographer Adam Galloway in the Netflix series House of Cards (2013-2014).