Due to internal wrangling at Warner Brothers, the decision was made to vastly cut down the running time after test screenings, reducing the 115-minute film to 87 minutes, sacrificing much coherence and continuity in the process. Key scenes removed included the opening sequence in which "Mrs. Peel" infiltrates and destroys the Prospero science installation; early trailers included the scene where she says the words "How now brown cow" in a false telephone box to gain admittance. The movie was originally scored by composer Michael Kamen, who included the original Avengers theme; however he was unable to re-score the film after the radical editing, so was forced to drop out. The recut version of the film was scored by Joel McNeely. The original shooting script was used for the film's novelisation and includes all the material shot and then removed from the film. The original cut has yet to surface; Warners are apparently not interested in releasing a director's cut or special edition in any form, even though director Jeremiah Chechik has offered to recut the film for nothing.
The "Training village" scene with Steed works much better as an opening (and probably comes closest to capturing the tone of the series), but that missing Evil Peel Twin opening clears up a LOT of confusion at the beginning of the theatrical cut--
Like, why is the Ministry treating talented-amateur Emma like a criminal from the start of the movie, why Steed automatically suspects her without evidence, how Real-Peel could know the secret phone password, etc., and just where the heck the robot/clone does show up from out of nowhere in the second half of the film.
Having watched The Avengers in the 60s, and then for decades in reruns, the movie was a huge disappointment. It was made by people who apparently had never seen the show.
The writers had seen the show, and did a thankless job of trying to capture the tone (although Patrick Macnee, in his "offscreen" cameo, still shows us how it was done). Even to the point of putting in that weird tribute to the three "Emma in the Maze" episodes.
Problem is, you had entire audiences who had never grown up on the series, thinking it was "some cool 60's spy series" like Man From UNCLE, and registered....nonplussment somewhat at a scene of villains dressed in teddy-bear suits, or grannies pulling machine guns out of their strollers. Kids, that was MILD compared to the series.
Biggest problem was the actors--I'm sure Ralph Fiennes has a sense of humor somewhere, but he remembered Steed as "mannered", and sleepwalked through the role, while Uma Thurman remembered Peel as "sexy", and snarled her way through. The writers capture a little bit of the Banter (and even a friendly swordfight straight out of their first episode), but the tone seemed to be lost on the actors and director somewhat.