Northern Ireland is routinely described as a divided society, and so it is.
But it is only at moments like the publication of the inquiry by Sir John Stevens into the killing of the Catholic lawyer Pat Finucane that you realise just how deeply divided it is, and how that division touches every aspect of political life here.
Sir John's report paints a shocking picture of how elements within British army intelligence and the Royal Ulster Constabulary collaborated with loyalist gangs on operations in which innocent Catholics were murdered.
Political allegiances run deep in Northern Ireland
Members of the loyalist gang who went to Pat Finucane's house in 1989 and shot him in front of his wife and children were informers, with army or police handlers.
So was the terrorist quartermaster who provided them with the firearms they used.
So was the paramilitary intelligence officer who told them where the Finucanes lived.
He was Brian Nelson, a former soldier sent back to his home city of Belfast by army intelligence to infiltrate the loyalist paramilitary Ulster Defence Association (UDA).
He ended up as a key figure in a shadowy set of relationships where some police officers and some army intelligence agents clearly sided with loyalist terrorists because they regarded themselves as having a common enemy in the provisional IRA.
So what of the political fallout?
This comes after all, at a time when the British and Irish governments have been making desperate, and so far unsuccessful, attempts to revive devolution ahead of next month's assembly elections.
Well, in truth the political fallout will be very limited, and as always here reaction will be more or less divided on sectarian lines.
He doesn't have the power to change the underlying attitudes of politicians here or the communities they represent
The veteran republican Alec Maskey survived a loyalist murder attempt during the period when this collusion was rife.
He told me that the whole episode should make people in the rest of the UK reflect on what was being done in their name.
It was, he said, state support for sectarian killing.
But Ian Paisley's Democratic Unionist Party in the build up to publication was already describing the Stevens investigation as propaganda designed to allow republicans to justify the murder of more than 300 police officers during the Troubles.
In other words, even the most significant developments in Northern Ireland tend to confirm politicians from the rival communities in entrenched positions... and so it will prove with the Stevens inquiry.
The allegations of collusion have provided a constant subtext to the troubles for even longer than the 13 years through which Sir John has been investigating them.
Nationalist politicians have said all along that elements of the security forces were collaborating with loyalist paramilitaries at the height of the Troubles.
Now that has been proved to be the case - although it should be remembered that many loyalist killers were caught and charged by those same security forces.
Unionists would argue that if the security forces made mistakes they made them under the pressure of a persistent and violent terrorist campaign in which their own members were often the targets for IRA attack.
Policing here has undergone huge changes in recent years and there are more to come, not least the possible addition to the policing board of representatives from Sinn Fein.
So the period of collusion should be safely in the past, allowing the Stevens inquiry to damn it on just about every possible level, as ineffective, as well as immoral.
Sir John has the power to recommend sweeping changes in the way the police in Northern Ireland conduct operations, and conduct themselves.
But he doesn't have the power to change the underlying attitudes of politicians here or the communities they represent... and in terms of local politics at least, that's the bottom line.