The series was commissioned by Lew Grade in the autumn of 1967. Pre-production was completed in October while the last episodes of "Captain Scarlet" were being filmed. Principal photography ran from 13 November 1967 to mid-August 1968 on the two puppet stages at Century 21's studios on the Slough Trading Estate in Berkshire. Each episode took an average of two weeks to film. The script for the first episode, "The Most Special Agent", was written by Anderson and his wife Sylvia as had been the case on earlier series created by the couple. Before WIN was devised, Joe was to have become the "Most Special Agent" of the CIA. Most of the episodes were written by Tony Barwick, with Shane Rimmer contributing six scripts. Rimmer was hired while co-authoring a book with Barwick, who initially offered him a two-script contract (these were filmed as the episodes "Splashdown" and "Big Fish").