It’s all about the roast beef sandwich. Ten minutes into Sidney Lumet’s seventies crime drama masterpiece we see the fresh faced, recently graduated Frank Serpico (Al Pacino) on his first beat as a uniformed New York cop. Stopping off for lunch in a greasy spoon diner with his assigned partner he’s introduced to the owner, Charlie, who lets them jump the line and offers up some cream of chicken soup.

Much to the grievance of Charlie, Serpico decides he’d rather have a roast beef sandwich. He’s new to the game, he doesn’t know the rules, the way things work. When the sandwich arrives it’s fatty and inedible. Just as he’s about to complain his partner stops him and gives him the low down. Charlie’s an ok guy, he gives the cops free food and they give him break on double-parking during deliveries. “Can’t I just pay for it and get what I want?” asks Frank. “Generally you just take what Charlie gives you,” his partner replies.

It’s the first hairline crack that will eventually lead to him watching his ideals and perceptions of what it is to be a New York law-enforcer gradually begin to shatter before his eyes. Frank looks down at his lean sandwich; it’s one of the small unofficial privileges that come with being in the NYPD, and it tastes like shit.

The real Francesco Vincent Serpico, known to his friends as Paco, has become part of New York folklore. A Korean War vet he joined the force in 1959 and eventually worked his way up to becoming a plainclothes policeman in and around Brooklyn and The Bronx.

Where as most of his fellow officers lived in the suburbs he lived downtown in Greenwich Village, the bohemian epicentre of the city’s counter-culture movement. A laid-back tea drinker surrounded by anxious and agitated caffeine fiends, looking more like the kind of person they usually arrested rather than an actual cop. He was loner, an outsider, and eventually a despised pariah within the force.

From 1967 onwards, along with another idealistic police officer named David Durk, he began a crusade against institutionalised corruption within the New York police force. But when the authorities that insisted on “cleaning their own laundry” continuously failed to take action he took his story to The New York Times, making the front pages in 1971. Serpico retired in 1972 after being shot in the face during an attempted arrest on drug dealers and left for dead by fellow officers.

When the story hit the headlines it caught the attention of hard-boiled investigative journalist and author Peter Maas. In 1969 Maas had become a household name when his seminal exposé of the Mafia, The Valachi Papers, became a best seller. It told the story of convicted informer Joseph Valachi, the first member of a mafia family to break their sacred code of silence and acknowledge the existence of a criminal underworld network known as the Cosa Nostra. It was later made into a film in 1972 starring Charles Bronson.

Serpico’s was a different kind of story, at the centre of which was a man of the times whose experiences reflected two epochal moments in American history that would define a generation, the assassination of John F. Kennedy and the shocking details that were gradually emerging in regards to the Watergate scandal.

They were profoundly significant incidents that instilled a deep mistrust of authority and an anxious paranoia over the American public. The message was that if you stood up for what you believed in and wanted to make a change for the good of mankind you would be killed, and the people in power were nothing but a bureaucracy of crooks cocooned in protective red tape. The illusion of common decency had been strangled to death in the common conscience.

With Serpico Peter Maas had another bestseller on his hands; one that personal business manager to the stars and former insurance salesman and nightclub agent Martin Bregman thought would make a great movie. As a manager Bregman had a number of big names as clients, including Barbara Streisand, Woody Allan, and a promising new face called Al Pacino. But Bregman wanted to become a producer and make his mark on cinema, and the story of Serpico gave him that opportunity.

First on board was scriptwriter Waldo Salt. Blacklisted during the McCarthy witch-hunts for being a member of the American Communist Party, after years of writing for TV under a pseudonym, Salt made a Hollywood comeback in 1969 with his screenplay for Midnight Cowboy. Although apparently brilliant his original draft for Serpico was far too epic in scope.

Norman Wexler was brought in to bring it down to an accessible length. Son of a Detroit factory worker, the deeply troubled Wexler was a manic-depressive who suffered severe episodes of psychotic mania, once resulting in imprisonment after he threatened to assassinate Richard Nixon whilst on an airplane flight. But despite his seriously unbalanced and unpredictable mental health issues he’d managed to carve out a successful career as a reliable scribe. His writing style was sparse and sharp; his dialogue was like a pounding rubber stamp of authenticity.

Wexler had received a Best Screenplay Oscar nomination for his work on another seventies classis, Joe (1970), the director of which was originally slated to helm Serpico. John G. Avildsen was a filmmaker with one eye on the counter culture’s effect on society and another eye on under the counter absurdity. His weird reflections of seventies mores were the kind of films that probably arrived in brown paper bags with strict instructions not to be screened during daylight hours, titles such as Turn On To Love (1969), Guess What We Learned in School Today (1970), and Cry Uncle (1971), one of the first films distributed by b-movie maestros Troma Entertainment and subsequently banned in Norway and Finland until 2003.

Due to artistic differences Avildsen was dropped from the project and replaced by another hired gun, Sidney Lumet. After years of directing in theatre and then moving onto television, Lumet made his stunning cinematic debut with the stagy but compelling courtroom drama 12 Angry Men (1957). He then drifted back and forth from television to cinema, from one genre to the next, occasionally making an effective impact with films such as Long Day’s Journey Into Night (1962), The Pawnbroker (1964) and The Hill (1965).

Lumet’s increasingly eclectic output continued throughout the seventies, beginning with a documentary on Martin Luther King, King: A Filmed Record (1970), frantic crime caper The Anderson Tapes (1971), and The Offence (1972), one of the most deeply unsettling and disturbing films of the decade featuring one of Sean Connery’s greatest performances.

Despite the occasional filmic misstep Lumet had established a reputation as a pragmatic, flexible, collaborative, socially conscious director with a meat and potatoes attitude towards filmmaking. He was an energetic straight shooter with a solid ability to tell a good story. But it was with crime dramas that he really hit his stride. There was something about betrayal and corruption that brought out the best in Lumet, Serpico being one of his greatest achievements, the quintessential gritty seventies New York crime thriller, and a worthy reminder that there’s no such thing as a free lunch.