In Northern Ireland things are never quite as they seem. Take Operation Banner, the British Army's 38-year deployment in Northern Ireland, which ended on the stroke of midnight last Tuesday evening. It was a historic moment, bringing the army's longest continuous operation to an end and leaving the police without military backup for the first time in nearly four decades.
Or did it? On Wednesday morning Banner was replaced by Operation Helvetic, which allows Sir Hugh Orde, chief constable of the Police Service of Northern Ireland (PSNI), to call in the British Army any time he deems it necessary. All that's required is a phone call to Nick Parker, the General Officer Commanding, and some of his 5,000 garrison troops will be freed up to support the civil power.
Padraigin Drinan, a civil rights lawyer, has pointed out that, should they be deployed again, the army will have some pretty chunky powers that are not available elsewhere in the UK.
They can stop and question at random. Anyone who refuses to provide soldiers with their name will face a fine of up to £5,000. The PSNI is the only British or Irish police force to enjoy the same power. It is also seeking powers to seize "special interest" material, such as journalists' notes, with a minimum of fuss.
Of course, nobody expects Orde to call the troops on to the streets again in any numbers. To do so would be seen as a big setback for the political process and the security situation. The province is well settled politically and the remnants of the para-military groups, both dissident republican and loyalist, seem so thoroughly infiltrated and so unpopular that it's hard to imagine them requiring a military response.
Unlike his predecessor, Orde would not need to consult Stormont or the Policing Board, though the board could scrutinise his decisions after the event. Compare that to the decision to call in the troops in 1969. That required high-level political discussion between Stormont ministers and their Westminster counterparts.
In one respect, these residual powers illustrate Northern Ireland's isolation as a region. They are the price being paid for the slimmed-down and highly regulated force that constitutes the PSNI.
Barring some new arrangement with the Garda Siochana, which would be difficult between two sovereign states, the PSNI cannot call on the help of neighbouring police forces in an emergency. It is natural, therefore, that the garrison is there for backup in the event that bombs need to be disposed of or to contend with a sudden security crisis.
One of the lessons of the recent conflict is that once a state finds it needs a power, it doesn't surrender it lightly. Another is that the price of transparency and accountability is the availability of another option that is not quite so transparent or accountable.
The availability of the army is matched by the construction of a vast new MI5 centre, the largest outside its London headquarters, at Palace Barracks in Holywood. While the PSNI's use of informants is strictly regulated and all its intelligence files are open to scrutiny by the Police Ombudsman, MI5 is not. It can call on police resources to help it with its task of infiltrating and monitoring both republican and international terrorist groups.
Nuala O'Loan, the outgoing Police Ombudsman who retires in November, is negotiating protocols with MI5 but these will be voluntary in nature and will not come close to her powers of oversight where the police are concerned. Naturally, the police will not necessarily be able to disclose information shared with them by MI5.
In a sense, these hidden arms of the state are the trade-off for the transparency and accountability that was negotiated by the Good Friday agreement and recommended by Chris Patten. That deal was accepted, if not enthusiastically agreed and endorsed, by Sinn Féin in its dealings with the British government and the Democratic Unionist party at St Andrews.
Over the years of Operation Banner, the interests of the British and Irish states and Sinn Féin have gradually converged. Captain Fred Holroyd, one of the first British intelligence whistleblowers to emerge in the Troubles, once recalled being told by an older officer at the Joint Services School of Intelligence in Kent, "to defeat the enemy you must first become the enemy".
It was, Holroyd was told, a lesson of Aden and other colonial trouble-spots that you must not only learn how your opponent thinks but also control his structures, shape his thinking and determine as much as possible who rises in his ranks and who dies.
By the time all the papers are released and the definitive history of Northern Ireland can be written, we will all be long dead. British intelligence and its army still guards the secret identities of agents codenamed Chalk and Granite who infiltrated the Irish Volunteers in 1916.
There are enough hints to suggest that sections of the apparently warring factions had a good deal more in common than they admit. We know of the MI6 line of contact to the republican leadership that existed since the early 1970s; we know about high-level agents such as Freddie Scappaticci and Denis Donaldson. We know too that lower-level ones, like Willie Carlin in Derry, pushed Sinn Féin's strategy towards elections and away from violence. We also know of the many British army officers and intelligence figures, like the senior MI6 analyst Michael Oatley, who came to empathise with the peace strategy of the republican leadership and to support their efforts.
Given that we know this much, we may guess that even greater levels of co-operation and collusion lie beneath the surface.
In his assessment of Operation Banner, General Sir Mike Jackson praised it as "one of the very few military operations] brought to a successful conclusion by the armed forces of a developed nation against an irregular force".
It wasn't a victory for the British Army but success is a fair description. Jackson's report describes Banner as a success for a strategy of manoeuvre and process and speaks of its lessons for other conflicts.
These are likely to be limited, however. Banner tied down up to 28,000 troops at a time for more than a generation, containing an area 120 miles by 80 with the help of thousands of locally recruited forces in the Ulster Defence Regiment and Royal Ulster Constabulary.
The size of the army, in relation to the area of operations, was such that it could easily stabilise the situation. After Operation Motorman, the massive troop surge that saw it take over the no-go areas in 1972, it was evident that the IRA would never control territory or have the possibility of victory. Once that was clear, it was simply a matter of bringing the political actors round.
That's the one lesson that can't easily be exported to Iraq or Afghanistan. It takes massive manpower advantages and half a lifetime to bring insurgents round to your way of thinking.