The programme's title comes from the Cockney rhyming slang term "Sweeney Todd", used to refer to the Flying Squad by London's criminal fraternity in the mid 20th century.

The part of Jack Regan was written for John Thaw, who was a friend of Ian Kennedy Martin, with whom he had worked on the TV drama series Redcap in the 1960s.

Ian Kennedy Martin saw the subsequent series as being mainly studio-based, with more dialogue and less action, but producer Ted Childs, inspired in part by Get Carter and The French Connection (both 1971), disagreed.

His role as series writer were filled by his brother Troy Kennedy Martin, Roger Marshall, Ranald Graham and Trevor Preston.

The series shows a somewhat more realistic side of police life, depicting them as flawed human beings, some with a disregard for authority, rules and the "system".

During the mid-1970s Flying Squad officers were publicly censured for being involved in bribery, corruption and for having excessively close links with the criminal fraternity.

Detective Chief Superintendent Kenneth Drury, the Flying Squad's real-life commander, was convicted on five counts of corruption and imprisoned for eight years.

He occasionally refers to his northern roots (his poor upbringing and his father's work on the Manchester Ship Canal), which prompts banter from George Carter, a Londoner, such as humming "The Red Flag".

Prior to the series timeline, the character had completed his National Service in the Signals Corps "in a minor intelligence role" (as revealed in episode 2.9 "Stay Lucky, Eh?").

In the first series Regan has a variety of drivers including Len (Jack McKenzie), Fred (Denis DeMarne) and Brian Cooney (Billy Murray).

As well as being the main squad car used to get Regan and Carter around London, it also features in the opening titles of series 1-3, driven by stunt man Joe Wadham.

One reason cited for the regular appearance of Jaguars is that they were favoured by the stunt drivers as being the "safest" cars to use (stuntman Peter Brayham devised the chases[10]).

According to Kevin Whately, John Thaw claimed that he had witnessed the regency red 1960 Jaguar Mark 2 (registration 248 RPA) used in Inspector Morse being written off several times while filming The Sweeney.

[11] A red Fiat 850 coupé (UJB 92G) makes cameo appearances in several episodes: typically, it is parked at the side of the road as the action takes place around it.

Carter's wife Alison (Stephanie Turner) is seen attempting to prise him away from the squad in episode 1.5 "Jigsaw", while her hostility toward Regan is apparent in 1.13 "Abduction".

Doreen Haskins (Sheila Reid) features in the penultimate episode 4.12 "Victims", which deals with her deteriorating mental health and the impact of police work on family life.

As well as the series title, other Cockney rhyming slang gave extra colour to the dialogue, including "poppy" (money), "bottle" (courage) and "grass" (informer).

This made it possible to shoot almost entirely on location for exteriors and interiors, helping to give the series a startling degree of realism and elevating London as a character of its own.

Directors Tom Clegg, Terry Green, Douglas Camfield, David Wickes, Mike Vardy and William Brayne were among the group of "guerrilla filmmakers" that realised the episodes.

What they and the crews delivered is a fast-paced series, depicting the squad's relentless battle against armed robbery; but it also includes a substantial degree of humour.

In Sweeney!, Regan and Carter become involved in a plot which shares similarities to the 1963 Profumo affair and British actor Barry Foster features as an American socialite loosely based on Stephen Ward.

On screen and in-film references include the line "The same damned speech you made in 1978" and a large banner at the OPEC delegates meeting features the convention's logo and the year "1979".

Regan and Carter are assigned the case as a last order from Detective Chief Superintendent Jupp (Denholm Elliott) before he resigns to face allegations of corruption in the courts.

[23] The 1993 Comic Strip film Detectives on the Edge of a Nervous Breakdown features a character introduced as "Shouting George from The Weeny" (played by Jim Broadbent).

A TV ad for the Nissan Almera car in the late 1990s had two characters similar to Carter and Regan racing through London to deal with a "bank job".

When they burst into the bank, it turns out that the men are genuine painters and that "Regan", their guv (or boss), is there to tell them they are using the wrong sort of white paint(!)

The boxset also contains exclusive extras, listed below: Regan: Commentary with Dennis Waterman, producer Ted Childs and director Tom Clegg.

Series One: Commentaries with Dennis Waterman, Garfield Morgan, producer Ted Childs, writers Trevor Preston and Troy Kennedy-Martin, directors Tom Clegg and David Wickes and editor Chris Burt.

Episode introductions by guest stars Warren Mitchell, Wanda Ventham, Prunella Gee, John Forgeham, Billy Murray, Tony Selby and Dudley Sutton.

Series Two: Episode introductions by guest stars Bill Maynard, Gwen Taylor, James Booth, Ken Hutchison and Lynda Bellingham.