To be a police officer in the Met in 1978, when my original TV drama Law & Order was broadcast on BBC Two, was to be corrupt. If you weren’t, you were likely to end up on the door of the Lord Chancellor’s office at the High Courts in the Strand. One policeman who refused either to play or become a whistleblower (“grass” in the parlance of the day) was cast out and made former Attorney General Michael Havers’ doorman.

Policemen in the 1970s were almost indistinguishable from villains in their accents, body language and fashion – and they were supposed to think in the same way, too. It was believed detectives needed to think like criminals to nick them. They were only smarter in that they got themselves a warrant card, giving them carte blanche to what was on offer.

Portraying such policemen on television then was shocking, especially to politicians who cried “foul!” Questions were asked in parliament about the parlous state of criminal justice. Led by Eldon Griffiths (representing the Police Federation), some called for me to be prosecuted for sedition.

Jim Callaghan’s government was incensed by these dramas, which didn’t stop at portraying endemic police wrongdoing, but also a corrupt legal profession, an extremely prejudiced judiciary, and sadists running our prisons.

Ian Trethowan, the BBC director general was summoned to the Home Office by the minister John Harris who was spitting mad, demanding to know why the broadcaster was making drama masquerading as documentary.

Trethowan argued they employed independently-minded producers who made well-researched drama. Harris warned that if the BBC wasn’t more responsible the Home Office would restrict its freedom.

Shows like Law & Order weren’t welcome.

Two years later, Trethowan didn’t resist Brian Wenham, controller of BBC2, scheduling a repeat broadcast. This occurred under Margaret Thatcher’s watch and Griffiths was more incensed.

Finally, “common sense” prevailed and Law & Order was locked away for 30 years, not even set free for television festivals, despite numerous requests.

Soon after the broadcast, with the dust of controversy still irritating Establishment eyes, work began on the Police and Criminal Evidence Act (PACE). This brought forth rules to safeguard the rights of suspects by requiring the prosecution to reveal its evidence to the defence before trial, and ushered in rules for police officers interrogating and charging suspects.

This was laudable, but brought added bureaucracy and limited the contact cops could have with crims.

The old adage prevailed: steal big and get a knighthood; steal a loaf of bread and get six months in prison.

How much has changed 40 years on from my series? The nature of wrongdoing has changed but, having built a better mouse-trap, the mice didn’t just get smarter – some turned into rats. And the doormen guarding “persons of importance” are now edgier, and more nervous of anyone approaching them.

Police officers are generally most efficient and successful in fiction, where the odd “bad apple” appears – while in reality it often seems to me as if they’re afraid of criminals, and tend to hide behind their computer screens. There are honourable exceptions, and the job remains dangerous and draining. Similarly, I hear of prison officers “scared” of prisoners.

But how could police officers, crown prosecutors and prison officers be expected to work better when nothing within society has shifted to cause them to change?

A lot of wrongdoers need to be prosecuted and imprisoned – a poor solution – but there can be no justice with what I see as a system so weighted against the accused. Only when we’re prepared to spend as much time and money to support the defendant’s story as we do trying to disprove it, only if we eradicate the apparent prejudice and fear that still exists in criminal justice, might we get a fairer institution.

That seems a remote possibility while finance continues to be cut, particular in law and policing. Lack of funding is a government, and a nation, saying: “We don’t care, we’re only concerned with the bottom line.”

We like to think a government of a different hue would do better, but none has proved so in the past.

Having spent 40 years trying to change hearts and minds, I’ve come to the conclusion that we can’t change anyone, only ourselves. However, I am optimistic about the swelling tide of compassion and the growing vegan movement. This represents true justice, true democracy, the future.

GF Newman’s Law & Order continues on BBC Four on Thursday 19 April at 10pm. His novel of the series is available as an ebook from No Exit Press.