“The Avengers” initially focused on Dr. David Keel (Ian Hendry) and his assistant (Macnee), but Macnee’s famously bowler hat wearing, umbrella-wielding intelligence officer (he never used a gun) became the protagonist when Hendry exited the series. Macnee played the part alongside a succession of strong, female partners, including Honor Blackman, Diana Rigg and Joanna Lumley. The show ran from 1961 and 1969 and was reprised in the 1970s.
The series was unsuccessfully adapted for the big screen in 1998 in a film that starred Ralph Fiennes as John Steed and Uma Thurman as his female partner and Sean Connery as the villain they faced.
Which goes to show how few ideas modern Hollywood has and how they always fuck it up when they think they can do better than the original.
This is a very early episode of the series, with Ian Hendry in it. The early episodes were on videotape rather than film:
Here is one with Diana Rigg:
There are a slew of these episodes on YouTube.