Michael O’Neill looked back on one of his best-loved roles in a conversation with TVWise: Special Agent Ron Butterfield, the head of President Bartlet’s Secret Service detail on The West Wing.

A recurring presence across the run of Aaron Sorkin’s political drama, Butterfield became O’Neill’s longest-running television role. The character sat at the centre of some of the show’s most tense hours, from coordinating the Secret Service response to the Rosslyn shooting that closed the first season, to breaking the news of Zoey Bartlet’s kidnapping in the fourth.

O’Neill also talked about the research that fed into the part, including what he picked up from the real US Secret Service about how its agents think, prepare and carry themselves, the kind of detail that helped ground a character who had to feel utterly convincing in a crisis.

Now a familiar face from shows including 24, Grey’s Anatomy, Bates Motel and Extant, O’Neill counts the West Wing role among the ones that shaped his path as a character actor.