Compared with the shock provoked by the revelations of a systematic police cover-up after the 1989 Hillsborough disaster, an ex-policeman's admission to Southwark Crown Court that he deliberately bungled 11 rape cases – faking records, falsifying witness statements and lying about forensic analysis – received relatively little attention. But Ryan Coleman-Farrow's case is chilling proof that Hillsborough is not an isolated aberration long in the past, but part of a decades-long pattern of unethical police practices which still continues today.

The past 40 years and more have been regularly punctuated by scandals involving the activities of the police. The list of cases casting doubt on the truthfulness and integrity of British forces is shamefully long, including the Birmingham Six, the Guildford Four, Blair Peach, Stephen Lawrence, Jean Charles de Menezes and Ian Tomlinson – to name but a few. Each incident has exposed toxic problems ranging from incompetence to racist stereotyping to outright disinformation.

There is an appalling array of examples from which to choose. There were, for example, the false claims that Mr Menezes, a Brazilian plumber shot dead by police on the London Tube, was a "suspected terrorist" wearing a padded jacket with wires sticking out. There was the Macpherson Inquiry into the Lawrence case, which exposed deep-rooted institutional racism in the Metropolitan Police. And there was the death of Mr Tomlinson in the G20 protests in 2009 and what the Independent Police Complaints Commission described as a "simply staggering" acceptance of ill-disciplined behaviour, given that the policeman who assaulted the newspaper vendor had faced complaints in two separate police forces but was still allowed to rejoin the Met.

Policemen and women are, of course, required to do a difficult and dangerous job. And it is one which requires a culture of loyalty, camaraderie and internal strength. But it too often results in unacceptable secrecy, in closed ranks, in obfuscation and dissembling.

In fairness, attempts are being made to remedy the situation. Not only are many chief constables working hard to instil a greater sense of integrity in their forces; the Government is also introducing elected Police Commissioners to boost local accountability, and one of the Home Secretary's more unpopular innovations is a plan to recruit senior officers from outside. But it will take more than a few tweaks to crack open the closed culture of Britain's police forces and re-shape a culture too wedded to the notion of protecting its own.

It will take more than a few tweaks to crack open the closed culture of Britain's police forces

The system for investigating accusations of malpractice is a good place to start, given that the more than 8,500 allegations of wrong-doing against the police over the past three years have resulted in just 13 criminal convictions. Even Dame Anne Owers, the new head of the IPCC, questions the ability of forces to investigate their own officers. She is right. The status quo would be laughable, were the fall-out from it not so appallingly serious.

But even that will not be enough by itself. The problems of police corruption will not end with either the Hillsborough report or the sentencing of Mr Coleman-Farrow. Indeed, one need look no further than the phone-hacking scandal for evidence of more to come. So far, attention has focused on the press. But the role of the police in selling information to newspapers is both more shocking and more corrosive of Britain's institutions.

It took the Leveson Inquiry to expose the behaviour and ethics of the media. The arguments for a full public investigation into the culture of the British police – perhaps modelled on the Hillsborough panel – are surely stronger still.