At the Royal Exchange Theatre, Manchester, he gave an "eye-catching",[1] "triumphant"[2] performance in the title role of Christopher Marlowe's Doctor Faustus in 2010.
In 2020, O'Kane had a significant guest role in the twelfth revived series of Doctor Who, appearing in three episodes as Ashad ("the Lone Cyberman"): The Haunting of Villa Diodati, Ascension of the Cybermen and The Timeless Children.
This gave him the distinction of being the first actor to play one of the programme's long-running Cybermen opposite Jodie Whittaker's thirteenth incarnation of the Doctor.
O'Kane has appeared in multiple plays written by Owen McCafferty, including Closing Time at the National Theatre in 2002,[6] Scenes from the Big Picture (playing a character who works in an abattoir rooted in the playwright's own experience) at the National Theatre Cottesloe in 2003,[7] and Shoot the Crow at the Royal Exchange Studio, Manchester in 2003.
The two did not collaborate as theatrical professionals until McCafferty began writing Closing Time while on secondment at the National Theatre Studio.