In the week that marks the 20th anniversary of the 1994 IRA ceasefire, new PSNI Chief Constable George Hamilton has delivered a "no going back" challenge.
And, speaking to this newspaper, he said the dissident republican factions "need to realise that the use of violence is not going to achieve their aims".
But he also spoke of the need for a "community and societal consensus" to deal with the past.
"The pain from the conflict that people suffered – that pain is still as relevant today as it was then and as a police service we want to acknowledge that," he told the Belfast Telegraph.
"Patten was silent on dealing with the past," he added, a reference to the report that introduced sweeping reforms across policing, including the end of the Royal Ulster Constabulary and the beginning of the PSNI.
And, in a challenge to politicians and communities, he said the issue of addressing the past cannot be left solely to the police and criminal justice system.
Mr Hamilton described "risk taking" and "generosity" as essential ingredients in the process of peace-building.
"We are almost celebrating the 20 years and, I suppose, it's right that we do," said Northern Ireland's top police officer.
"But let's not forget that the entire 20 years has been a bumpy ride.
"Let's not forget that in February 1996, the ceasefire broke down; in June 1997 the murder of two police officers, and many other incidents.
"People took risks and stuck with the concept that this is a process.
"I think it's incredible that we had two police officers murdered in June 1997 and yet we had the Good Friday Agreement in April 1998.
"That's credit to the political leaders – taking risks, showing generosity for the greater good."
But, 20 years on from the ceasefires, his message is there is still more to be done – specifically on trying to answer the vexed questions of the past.
"Those ingredients of risk-taking and generosity are still key in terms of keeping the momentum of the peace process going," he said.
"We now have, with one or two exceptions, we now have the realisation of the Patten template.
"We want to get to the point where policing is about the things that are of most concern to society.
"Like tackling child sexual exploitation, hate crime, domestic violence, anti-social behaviour at community level, human trafficking."
But tackling the violent dissident republican threat and other challenges linked to contentious parades remain a distraction in terms of policing objectives.
Twenty years on from the ceasefires announced by the IRA and the Combined Loyalist Military Command in August and October 1994, the dissident threat, marching and an unanswered past represent the unfinished business of the peace process.
"The key thing is there is no going back," Mr Hamilton said.
"Those who did not subscribe to the decisions taken by mainstream republicans need to realise that the use of violence is not going to achieve their aims."
"Disagreement with mainstream republicans or unionism is fine with policing," he added.
"As long as their activities are within the law."
He pointed to the significant changes in the security landscape achieved in the past 20 years since 1994.
Not just the structural reforms brought about by the Patten Report, but the dramatic demilitarisation of Northern Ireland.
In August 1994 police and Army numbers were in the region of 33,000. Today, the PSNI figure is 6,700
And two decades after the IRA announced its "complete cessation of military operations", those figures represent part of what has changed and what is different.
No such thing as a perfect peace, and end of road is still not in sight
You have to look at other world conflicts to put the peace process here into its proper context.
Up until 1994, when first the IRA and then the Combined Loyalist Military Command (CLMC) announced ceasefires, the Northern Ireland story was told in headlines of bombs and bullets.
But those tentative steps 20 years ago began to change things.
Attending the funeral of former Taoiseach Albert Reynolds, Martin McGuinness acknowledged the “crucially important” role he played in those developments two decades ago.
“His courage in initiating political dialogue as an alternative to conflict is a model that should be followed across the world,” McGuinness said.
And, of course, the now Deputy First Mminister was a key influencing voice in those internal IRA debates in the build-up to the announcement of the “complete cessation of military operations”.
The new Chief Constable George Hamilton has rightly identified the flaws both in the republican and loyalist ceasefires, and set the context of a process — after conflict, peace is not delivered in an instant.
George Hamilton was an inspector in 1994, one of 13,500 police officers supported by 19,500 troops in Operation Banner.
The IRA's bunkers were stuffed with Libyan-supplied weaponry.
The ceasefires were delivered not in the context of victory and defeat but the acknowledgement of stalemate and, to quote one republican, “the moral obligation to explore the alternative”.
Ceasefires were a beginning, not an end. Much more significant was the IRA statement of 2005 formally ending the armed campaign and signalling further moves to put arms beyond use.
“You can't get any more final,” that senior republican commented, as he identified the choices of politics or community work given to those who had been part of the IRA. Similar statements came later from loyalists.
But there is no magic wand that makes the past disappear, no such thing as a perfect peace and no full stop for the final end.
The Chief Constable has also identified what still needs to be done — the unfinished business of peace-building. You see it in the dissident threat, in the continuing need for MI5 intelligence, in the battles over the past and where parades meet protests.
The project that is called “new policing” is also a process, at times still mired in the mud of the Seventies, Eighties and Nineties.
How much of the past will be excavated and explored, how much of the so-called dirty war will be shown and seen, we don't know.
But George Hamilton has deliberately raised the issue of the past at this time because it is a rope that still pulls policing back.
The past is not just about the police and the criminal justice system, but those wider processes identified in Eames/Bradley, in the Haass/O'Sullivan texts and in proposals put forward by the Victims’ Commissioner.
And, in carefully chosen words, the Chief Constable is both challenging and reminding the politicians.
He is acknowledging what has been achieved but also identifying what still needs to be done.
What he is saying, and what others know, is that even after 20 years, the journey is not yet complete.
Timeline to anniversary of ceasefire
August 1994: IRA announces “complete cessation of military operations”.
October 1994: Loyalist CLMC announces it will “universally cease all operational hostilities”.
December 1994: Government officials begin exploratory dialogue with Sinn Fein and loyalist political parties.
February 1996: After long stand-off on decommissioning, IRA ceasefire collapses with London Docklands bomb. Breaches of loyalist ceasefire follow.
May 1997: Tony Blair wins landslide General Election. Following month Bertie Ahern becomes Taoiseach.
July 1997: IRA ceasefire restored, leading to negotiations and Good Friday Agreement in April 1998.
June 1998: Assembly elections
September 1999: Patten report signals sweeping reforms across policing.
July 2005: IRA orders end to armed campaign. Within days it is announced Army's Operation Banner would end July 2007.
May 200: UVF and Red Hand Commando announce organisations to “assume a non-military, civilianised, role”.
May 2007: Ian Paisley and Martin McGuinness become First and Deputy First Ministers.
November 2007: In statement, UDA says it “believes that the war is over”.