The quintessential "escapist" British action series, the weekly, hour-long The Avengers debuted January 7, 1961, as an outgrowth of Police Surgeon, another series produced by the U.K.'s Associated British Corporation (later known as ITV). Although Police Surgeon was not a hit, its star, Ian Hendry, scored a personal success in the leading role of Dr. David Keel. The decision was made to rework Police Surgeon, changing it from a traditional action-adventure program to an espionage drama. This was accomplished via a rather gruesome plot twist: David Keel's wife was murdered by a vicious drug ring, compelling the protagonist to join forces with professional secret agent John Steed (Patrick Macnee) to bring the criminals to justice and avenge his wife's death -- hence the new title, The Avengers. As the "new" series' first season (originally telecast live, then videotaped) rolled onward, it was clear that the viewing public was responding more positively to the character of John Steed than to David Keel. Although well versed in deadly weaponry and the manly art of self-defense, Steed was the "perfect" Englishman: polite, soft-spoken, wryly humorous, and seldom seen without his bowler hat and umbrella. Gradually, David Keel was written out of the series and other actors were tried out in the role of Steed's partner, including Ingrid Hafner as Carol Wilson.

During The Avengers' second season, Steed was provided with two alternating female partners, both "talented amateurs" who worked as spies only on a part-time basis: Venus Smith (Julie Stevens), a nightclub singer, and Cathy Gale (Honor Blackman), a widowed anthropologist with a talent for martial arts and a charming predilection for wearing form-fitting leather outfits. Also, Jon Rollason made a handful of appearances as Dr. Martin King, a character designed to replace the departed Ian Hendry. As it turned out, only Cathy Gale truly "clicked" with the viewers, and as a result she became Steed's permanent partner. The implicit kinkiness projected by the leather-clad Mrs. Gale, coupled with the relaxed, double-entendre badinage between the two protagonists, not only suggested that Steed and Cathy enjoyed something rather more than a professional relationship, but also moved the series away from its relatively serious and realistic beginnings and pushed it toward a more humorous, "campy" direction.

Once it became obvious that The Avengers was even more popular as a larger-than-life satire of the espionage genre than as a "straight" action series, the writers began adding elements of science fiction and the supernatural into the proceedings. Although The Avengers had gained an international reputation by the time the series ended its third season, the series had not yet been shown in the United States. However, the "spy craze" engendered by such series as The Man From U.N.C.L.E. prompted America's ABC network to begin telecasting The Avengers on March 28, 1966, by which time the series had entered its fourth season and Honor Blackman had left the show. Blackman's replacement was Diana Rigg in the Cathy Gale-like role of Mrs. Emma Peel, who like her predecessor was a spy only in her off-hours, specialized in martial arts, and evinced a fondness for leather clothing and tight pantsuits. A bit more aloof and standoffish than Cathy Gale, Mrs. Peel was nonetheless just as adroit with a clever quip or ironic comment -- and like Cathy, she was completely unfazed by danger, reacting to the many perilous situations in which she was placed with cool, calm, and utterly British reserve.

Having already switched from videotape to film in its fourth season, The Avengers switched from black-and-white to color during season five, at the behest of its American distributors. Although the added cost of color would ultimately result in a pronounced lowering of production values, the fifth and sixth seasons proved to be the most popular in The Avengers' history -- not to mention the most outrageous in terms of plotlines and over-the-top villainy. The beginning of season seven marked the departure of Diana Rigg (it was explained that Mrs. Peel's long-lost husband had been located, compelling her to retire from active duty), and also several shakeups within the series' production staff. The format was revamped, eliminating most of the series' campiness and returning to more standard action-adventure fare. At the same time, it was decided that Steed's new female partner, greenhorn spy-school graduate Tara King (Linda Thorson), would be less self-reliant and more vulnerable than her predecessors. Finally, Patrick Newell was added to the cast as "Mother," a corpulent, wheelchair-bound gent who, as Steed and Tara's immediate superior, popped up in the unlikeliest places and issued orders in the most imperious and annoying manner possible. Although most dyed-in-the-wool Avengers fans disliked the many changes made in the series, its final season yielded more episodes (32 in all) and generated more international revenue than in any previous year.

Canceled by Britain's ITV on September 14, 1969, and by the U.S.'s ABC one day later, The Avengers was revived in 1976 as The New Avengers (later retitled The Avengers Forever). Patrick Macnee was back as John Steed, with Joanna Lumley and Gareth Hunt as his new secret-agent associates Purdey and Gareth. During the next decade, several of the old Avengers episodes starring Honor Blackman (originally videotaped, but available only in kinescope form) were broadcast in America for the first time; and in 1998, Uma Thurman and Ralph Fiennes starred in a theatrical-movie "remake" of The Avengers, which also featured Patrick Macnee in a voice-over cameo.