The Sweeney focused on the exploits of Jack Regan, a maverick detective inspector (D.I.) attached to the Flying Squad, the metropolitan police's elite armed­ robbery unit, and featured John Thaw in the leading role. The program, which derived its title from "Sweeney Todd," the Cockney rhyming slang for "Flying Squad," was a spin-off from the successful 1974 TV film Regan, which had first introduced the protagonist and established his professional relationships with his assistant, Detective Sergeant (D.S.) George Carter (played by Dennis Waterman) and his "governor," Detective Chief Inspector (D.C.I.) Haskins (played by Garfield Morgan). Each episode in the series adopted the same basic narrative format-a three-act structure (with acts separated by advertisements) preceded by a prologue that triggered the crime narrative. The first two acts were devoted to obtaining intelligence about a forthcoming robbery, often through tip-offs from informants or surveillance; the third involved the capture of the robbery gang, characteristically involving adrenaline-pumping action with car chases, screaming tires, spectacular smashes, and hand-to-hand fighting. The narrative was often further complicated through the addition of an anti authority thread in which Regan challenged Haskins's "rule-book" approach or through the introduction of casual sex relationships in which one of the detectives became involved with an available woman.

     The program's realism was considerable, and few other crime series have achieved so authentic an impression of the policing of London's underworld. To an extent, this was achieved by adopting the same visual style, fast action, and cynical outlook as contemporary rogue-cop films, such as Dirty Harry and The French Connection. Equally, though, the program relied on detailed inside knowledge of the actual circumstances in which the Flying Squad operated and the sometimes rather dubious means used to secure prosecutions. The series' storylines frequently blurred the sharp distinctions that are normally drawn between good and evil characters in crime melodrama. Regan and Carter were shown inhabiting the same sleazy world as the criminals, mixing with low-lifes to obtain their leads, and adopting the same vernacular. Both law enforcers and lawbreakers indulged in womanizing and heavy drinking and used  physical  violence to achieve their objec­tives. The extent to which Regan was prepared to bend and break the rules to "nick villains" was well established in the pilot film, when he threatened a suspect with a longer sentence if he did not cooperate: "My sergeant is going to hit me, but I am going to say it's you." Throughout the series, however, the viewer's sense of Regan's integrity remained secure. Even though he might need to beat up suspects, strike deals with criminals, or, on one occasion, burglarize the office of the D.C.I. to read his own personal file, such ac­tions were legitimized in the narrative as the only means available to the serious crime fighter to keep on top and to cut through the dead weight of bureaucracy that continually threatened to impede the cause of justice.

     Unsurprisingly, the series provoked fierce controversy, chiefly because of its potential to influence the public image of the police at a time of considerable social upheaval. However, the dark (if not confused) moral world that the series represented was difficult to fault on purely realistic grounds since, at the time of transmission, a prominent officer in the Squad was under investigation and was eventually imprisoned for corruption. Considered in wider cultural terms, the program has been viewed as part of the general ideological shift to the right that occurred in the 1970s in Britain, as the postwar social-democratic consensus broke down. James Donald, notably, has argued that The Sweeney was fueled by popular anxieties about law and order stimulated by the press campaign on mugging and that episodes provided a "mapping fantasy" for the acting out of unconscious authoritarian urges.

The Sweeney had sold to 51 countries by 1985 and inspired two successful feature films. It also established Dennis Waterman and John Thaw as household names with the British public. The series secured the reputation of Euston Films as a leading production company, and it created an influential model in Britain not just for crime series on ITV but for the production of cost-effective, high-quality drama in general. The lean and efficient production operation that Euston pioneered in The Sweeney, relying on short-term contracts and shooting entirely with 16-millimeter film, has been generally adopted across the industry; with the exception of soap operas, the great majority of drama projects today are manned by freelance crews and produced on film.