By Brian Rowan
BBC Northern Ireland security editor
There is no number for the IRA in the telephone book, so General de Chastelain has to wait for the call that will tell him whether there will be work for him this Christmas.
That will depend on the outcome of the long political negotiations that have spanned a period of some months, but which are coming to a close.
General de Chastelain will have to wait for the IRA's call
Soon it will be decision time and, soon, we should know whether Ian Paisley and Gerry Adams are able to do the deal of all deals.
The British and Irish governments are still waiting for responses from the DUP and Sinn Fein to a proposed way forward set out in a document: Northern Ireland: Outline For A Comprehensive Agreement.
There has been plenty of speculation about what the IRA will say and do in the context of any comprehensive agreement, but that organisation has not yet spoken for itself and nor has it met recently with de Chastelain's Independent International Commission on Decommissioning (IICD).
Ian Paisley has, but he did not get the answers he was looking for, and nor should we be surprised at this stage of the negotiations.
The IRA is not going to sign on any dotted line until it is sure about the outcome of the political negotiations, and the DUP is not going to give its verdict on the British-Irish government paper until there is "certainty" about the IRA intentions.
So, not for the first time in this process, there is a stand-off over guns and government.
The big DUP demand on decommissioning is for photographic proof - and proposals on how this should happen are set out in the British-Irish paper.
They are proposals from the governments, and there is no information yet to suggest that republicans have agreed to or will consent to what is suggested.
What we do expect from the IRA - if a deal is done - is the most significant acts of decommissioning so far.
According to talks sources, these would occur between now and the end of December, and they would be witnessed not just by de Chastelain and his IICD colleague Andrew Sens but by two churchmen - one Catholic and one Protestant.
The IRA is expected to put its weapons beyond use
This is something new in the decommissioning process - additional watching eyes, new voices to tell the story of how the IRA put its arms beyond use.
And for republicans this is a huge concession.
We would also expect de Chastelain to report that he has overseen the decommissioning of all IRA weapons, and the IRA would say in its own words that all activities are ending.
What is being suggested here is an end to "physical force" republicanism set in the context of a comprehensive deal - an agreement which would have power-sharing politics, new policing arrangements and sweeping security changes.
In a weekend interview, the Sinn Fein president, Gerry Adams said: "Say we get to the point where we have a comprehensive agreement, and say we get the IRA, that it is prepared to put weapons beyond use, and is prepared to go into entirely new mode, and we're all satisfied we are going to see in this time of our lives perhaps an end to physical force republicanism, is it going to be thrown away because Ian Paisley doesn't get the process of humiliation that he wants?"
Not that long ago, any deal in the context of an agreement between Paisley's party and republicans - would have been dismissed as "unthinkable".
But the DUP won't move, won't agree, won't give its verdict on the proposed way forward set out by the governments until it knows exactly what the IRA is going to do.
The party wants confirmation that the new decommissioning witnesses will be allowed "to see and speak", and they want republican "clarification" on the issue of photographic proof of decommissioning.
In a nutshell, their question is: Will photographs be taken and will they be published?
"We need absolute certainty that there will be no restrictions on what the witnesses will be able to see," the DUP deputy leader Peter Robinson told me.
"They can't be gagged when they come back and, equally, there's no point having photos if nobody is going to see them. We need certainty. We are not going to make assumptions," he added.
The suggestion in the proposals made by the governments is that the photographs are taken at the time of decommissioning in December.
They would be held by de Chastelain and not published until March - the target date for devolution and for a power-sharing executive that would include DUP and Sinn Fein ministers.
Peter Robinson said the DUP cannot make assumptions
That is what is proposed, but, in the background, some DUP members are still pressing for earlier publication.
But what if there are no photographs, and what if the IRA says no?
There is nothing to suggest that the governments wrote their proposals based on firm promises from republicans.
So were they written more out of hope than expectation?
This issue of photographic proof is still a potential deal breaker.
What the DUP sees as a necessary confidence-building measure, is viewed by republicans as an attempt to humiliate the IRA.
So we don't yet know how this most difficult issue will be settled.
Will republicans offer something more than the witnesses?
Will the DUP settle for something less than the photographs?
On Monday, when Ian Paisley goes to Downing Street for another meeting with Tony Blair, he will travel not with an answer but with more questions.
At the same time other senior party members will be meeting government officials.
The DUP and republicans are very close to a deal, but it could all still trip up - not over the extent of IRA decommissioning but on the issue of visible proof.