In December 1974, at the height of The Troubles in Northern Ireland, four people were arrested for bombing the Guildford Pub. Four people died in that bombing, 65 were injured, and Britons were left feeling unsafe not only in their beds, but most other places as well.

Those arrested came to be known collectively as the Guildford Four. That they did not fit the typical profile of IRA terrorists was of no moment: there was enormous public pressure to secure both arrests and convictions when it came to the Provisional IRA.

Indeed, two of them were living in a squat, one had what in normal circumstances would be a cast-iron alibi – she was at a rock concert – and another just happened to be visiting his aunt in London. They were Irish, and that was all that mattered: the arrests gave form and substance to the old joke about “innocent until proven Irish”.

Under legislation just passed, the police could hold people without charge for a week, rather than the usual 48 hours, and did not have to act on “reasonable suspicion”. At the same time, use of suspect interrogation techniques – ranging from intimidation (threats to family members and mock executions) and the infliction of pain (typically, ear-twisting) – had become routine not only in the Royal Ulster Constabulary, but had spread to forces with better reputations, including the Met.

Under torture – torture that left no marks, and caused no injury – everyone confessed, either to bomb-planting or making explosives. All four served sentences of between 15 and 16 years, except for Patrick Conlon, who died in prison. And the only reason the Guildford Bombers were released was because it became clear that the confessions – all of them false – had been obtained under torture.

The police had also fabricated evidence when torture proved ineffective at extracting sufficient detail: people in pain tend to produce stories lacking the colour and movement that persuades courts and juries.

In 1989, long after this gross miscarriage of justice, the convictions were quashed. Those still incarcerated were released. In 2005, Tony Blair finally apologised, saying “I am very sorry that they were subject to such an ordeal and injustice... they deserve to be completely and publicly exonerated”.

In Australia, in 2014, Attorney-General George Brandis’s National Security Legislation Amendment Bill will grant immunity from civil and criminal liability to participants in special intelligence operations. Asio agents, and anyone else listed as a participant, will not be able to kill, inflict serious injury, or commit a sexual offence. But nothing will prevent them, Australians all, from doing what was done to the Guildford Four. Worse, Brandis’s Bill proposes to gag journalists and bloggers if they tell anyone, with a 10 year gaol term if they do.

Every time the state wants to curtail liberty in the name of security, it seems people like me have to stand up and shout how badly this can go wrong. Many Australians – like many Brits during The Troubles – seem to operate under the comforting illusion that we in liberal democracies are all decent people and can undermine our institutions with nary a thought as to the long term consequences. We seem to think our natural good intentions will prevent us from coming to resemble those against whom we fight.

There is no such thing as natural good intentions. The reason we don’t butcher each other in the name of a religious ideology, like our Islamist enemies, is not because we are special examples of the human – intrinsically better than Isis or Hamas or the Provisional IRA.

Rather, we are better because our institutions and civic culture are better, things that had to be built up over centuries, even millennia. As early as the third century AD, the Roman jurist Ulpian observed that not only did torture produce false confessions, but even when it “worked”, it was institutionally corrupting.

Without the benefit of laws permitting extra breaches of our civil liberties, Asio and the AFP have apparently just busted up a terror cell. If we are in the business of defending liberal democracy, then we must fight freedom’s cause in freedom’s way. I do not wish to see “innocent until proven Muslim” in my country. And Australia’s air is too pure for torture.