Cult Spy Icon: Kellerman ('Prison Break')

Nothing seems permanent in Prison Break. There's Sara Tancredi’s 'temporary' death by decapitation, plus Scofield's entire upper body tattoo being easily removed and the characters' general unwillingness to stay in any cell for too long. But in terms of character transitions, Agent Kellerman wonderfully represents the ability to shift from one side of the fence to the other, while never losing his dark morals along the way.

Paul Kellerman, with a strong chin that defies his soft eyes, was initially a clear-cut villain, mercilessly stalking his prey on behalf of The Company and barely showing any flicker of emotion when killing anyone. He worked tirelessly to prevent those trying to uncover the truth about the wrongly convicted Lincoln Burrows, who was precariously perched on Death Row.

He was at his worst early on in the first season when he baited poor LJ after causing his mother's death, displaying an enormous amount of callous cruelty. His loyalty was firmly geared towards Vice President Caroline Reynolds, and this compelled him to kill his own partner Hale when he threatened to jump ship.

The second season brought forward more atrocious acts, particularly his befriending of the vulnerable Sara Tancredi by posing as a fellow addict. It wasn't long before he was trying to drown her in her own flat in a bid to locate the escapees Scofield and Burrows.

The list of his unforgivable misdemeanours could go on. Yet, somehow, the booing and hissing that used to greet his appearance eventually gave way to cheers. For Kellerman became the show's defining anti-hero when, having been cut out of the Company loop, he grew disillusioned and vowed to help the brotherly heroes exact vengeance on his former employers.

This was a fairly sudden shift, given his previous desperation to make them suffer and die, but it felt convincing due to actor Paul Adelstein’s brilliance in the role. Some clever writing for the character, including a botched suicide attempt and revelations of a fraught family background, helped to engineer some new pathos towards Kellerman.

At the end of the second season, Kellerman was accosted by Company men while in police custody having given damning evidence against his former employers and completed his remarkable transition from villain to hero. He was apparently killed off-screen, as gunshots were heard, but in the world of Prison Break seeing and hearing is not the same as believing. Only time will tell if Kellerman emerges again… and whether he is fighting for the right side.