The greatest trick the devil ever pulled was to convince the world he didn't exist. Let me show how this iconic line from the film The Usual Suspects applies to Northern Ireland.

John Hume's peacemaker legacy is under threat from republican revisionists. I have a loose connection with the Nobel Laureate. He studied at Maynooth. I lecture there for the Edward M Kennedy Institute in a part of the university named after him. The Maiden City's famous son and the late US Senator were friends. Their relationship did much to expose the IRA "freedom fighter" myth in Irish-America.

John Hume championed equality and a fairer society. The civil rights movement shows this. Unfortunately, it was sectarianised by burgeoning Provos. These were hate-filled agents of chaos, who used the movement to cause violent confrontations with the police.

Hume wanted to reform the state. They wanted to destroy it. Their first step was to get control of republican areas by forcing the police out of them.

The next was to attack the "other side". And the main objective thereafter was to undermine the rule of law.

This is how a violent insurgency forms its base. It is simple stuff and deeply sectarian.

The Troubles were due to a failure in politics, not a failure in security. No nationalist, or unionist, party is blameless. Neither London nor Dublin comes out of it well.

Of Hume's SDLP, Gerry Fitt complained that it got too close to the Provisionals. Conscious of this, Hugh Annesley, in his chief constable's annual report of 1990, said: "Anything less than real support for the police carries with it the prospect, indeed certainty, that violence will continue to afflict us all."

In other words, it was not enough for the SDLP to condemn IRA murders of police officers, which Provisional Sinn Fein excused; it had to support the police. This never happened.

Yes, the police made blunders that angered nationalists. But this needs to be balanced against unprecedented levels of violence and a force that was turned around by 1976 and made fit for purpose by reforming chief constables.

A royal prefix and being mostly Protestant did not equate to bias and bigotry. Based on the early release of terrorist prisoners in the Belfast Agreement, the RUC was tougher on loyalist paramilitaries than republicans.

As for Catholic officers, how did the SDLP's stance help them, or their families, or encourage other Catholics to join?

To be fair to Hume, by the time he headed the SDLP, the Provo propaganda machine was in full swing. Nothing of this magnitude, or sophistication, had been seen before. The state was clueless in response.

The Provos did a masterclass in misrepresenting the RUC's British symbols to taint it as a sectarian instrument of British imperialism. Also denigrated in the process were Orange culture, the Protestant community and everyone who supported the rule of law and security forces.

Fake news and spin influenced nationalist opinion of the RUC more than facts and outcomes. This, and keeping both communities divided and distrustful of each other, benefited the Provos.

Police officers were dismayed at nationalist leaders who shouted about not getting normal policing and then worked against its delivery. It was the great dilemma of the Troubles; normal policing was the last thing the IRA wanted, but the hardest thing to pull off.

The SDLP seemed oblivious to this, and did itself no favours by sharing Left-wing policing concepts detached from reality.

In local politics, there was an absence of common purpose. Nationalists and unionists did not get on.

The political shortfall put extra pressure on the police, although the SDLP did not appear to make the link.

Indeed, it was sensitive to claims that its position increased the risk to officers and public safety and was less animated by security force personnel killed by republican terrorists than the other way round.

Hume's intent was honest. He wanted to do the right thing. It is a pity - unlike Fitt and some other nationalists - he did not see these qualities in the police.

In the Belfast Agreement, nationalism and republicanism united in demanding the RUC's disbandment and singling it out for a law to retrospectively investigate it.

A new criminal justice arrangement ensured a steady flow of criticism of the security policy. For nationalists, the subtext says, it was right not to support the police. And, for republicans, it says, the "armed struggle" was justified. They complement each other, which is what annoyed Fitt.

I doubt the one-sided approach that materialised and its divisiveness is what Hume had in mind. But it is what the Provisionals had planned for.

On the past, a "peace process" focused on security largely leaves politics and the Provos alone. It has made it easy to forget that the majority of the population supported the police and that the Provos were the main protagonist.

In the eyes of the two governments, this is pragmatic politics. For many people, particularly those touched by terrorism, it is a sordid sham.

The science of irregular war tells a different tale. It deals with preventing conflict and what prolongs it. An example is passive support, vital to a terrorist network.

This is topical in claims that moderate Sunnis in war-torn nations sympathise with co-religionist jihadists and do not back the security effort. The US and others, as with Annesley before them, found this a major obstacle to ending armed conflict.

Violent insurgency is an iceberg. It is more than terrorism and headlines.

Provo historians are promoting their leaders as peacemakers and hiding Hume's legacy, much to the annoyance of the SDLP.

The screening of a documentary sympathetic to Hume, In The Name of Peace, at the Galway Film Festival highlighted the issue recently. But what did the SDLP expect of Sinn Fein?

For 20 years, terrorism's true face has been masked at the expense of a fine police force with no complaints from nationalist politicians and no interest from documentary-makers.

It's as if the IRA never existed.

William Matchett is author of Secret Victory: The Intelligence War that beat the IRA. He is a senior researcher at the Edward M Kennedy Institute for Conflict Prevention at Maynooth University

Belfast Telegraph