Callan (1974)

Callan's was a violent, bleak world where if you didn't kill first — they killed you. He was a cold-blooded killer, an outsider — isolated, often in direct conflict with his superior Hunter, a codename given to all Heads of Section.

So successful was the hit-man with viewers that author James Mitchell was asked to write a series that went on to become one of the most successful programs in British TV history running from 1967 to 1972.

Callan made stars of the two central performers, Edward Woodward who played the disaffected agent and Russell Hunter, as the snivelling, smelly, petty thief Lonely, the spy's accomplice.