After years of guest-starring roles, Woodward's first big TV break was in this rule-breaking series about an embittered, broken spy who also serves as the top assassin for British counterintelligence.

It gave Woodward a chance to show his true range.

"On most TV programmes there are one or two things that come up that concern you, things you're asked to do that you don't feel entirely comfortable with, and Callan was no exception, but it was such a well written series, rather than try to change anything, I just tried to rise to the challenge of performing it," he's said of the show.

"Back when it started, we didn't know if the programme was going to work or not. Callan was such an extreme character for the time. But it was a risk that paid off. It gave my career a huge boost, first nationally, then internationally. Really Callan was the key to my whole life and career."