Pakistan's 'loose nukes'
Every now and then in this business someone in a position to know some enthralling secret passes information on to you, but you have no means of backing it up from other sources.
A few years ago, I was told about extraordinary US contingency plans to recover Pakistan's nuclear weapons, in the event of a collapse of law and order or an extremist coup in that country.
My informant gave me considerable detail. A super-secret agreement had been put in place early this decade following confrontations between India and Pakistan, two nuclear armed nations, over the disputed Kashmir region.
In order to stabilise an otherwise potentially highly volatile situation, Pakistan would tell the US where its nuclear weapons were.
India had been promised, that in the event of some Pakistani national cataclysm, the Americans would move in to remove the nuclear weapons.
The "loose nukes" nightmare would thus be avoided, and India would not be tempted into a first strike on Pakistan's atomic arsenal.
Sometimes stories, even from people who have held senior positions in Western governments, are a little too good to be true.
This one seemed to smack of Tom Clancy. Nobody would ever confirm it, and indeed some of those I checked it out with were openly sceptical. So I never ran the story.
Perhaps, after all, my original informant had been trying to plant it.
Now that the Obama administration is openly voicing its concern about the threat to Pakistan's nuclear weapons from rising militancy in that country, some aspects of that original tip off have come back into sharp focus.
In April, Secretary of State Hillary Clinton told a US senate committee, that the US spent a lot of time worrying about Iran getting nuclear weapons, but that Pakistan already had them, and that, "they've adopted a policy of dispersing their nuclear weapons and facilities".
In this phrase, "adopted a policy" I detected a possible inference that Pakistan had moved away from an earlier procedure of keeping their bombs in a small number of locations.
My further inquiries suggested this inference was deliberate.
So here at last was a measure of confirmation for something I had heard years earlier.
As to what exactly Pakistan had told the US in the time of president (and former army chief) Pervez Musharraf, we are once again in hazier territory.
We do know however that Mr Musharraf knew far more about the country's nuclear complex than any civilian leader has ever been allowed to learn.
We also know that in the first years after 9/11, there was intimate strategic co-operation with the US.
Of course any suggestion that the US might, in the past, have had plans to sweep up these weapons is politically sensitive in Pakistan.
The country revels in the status that its arsenal has given it. Any suggestion that there were plans to "secure" the bombs, even in a state of anarchy, would strike many Pakistanis as a US plot to emasculate an Islamic nuclear power.
Some feel the nuclear danger is being exaggerated in Washington in order to build support for the Obama administration's Af-Pak policy.
There may be something in this, given that the chance of Taliban storming some nuclear weapon storage point is remote.
But the real danger at present lies in subversion.
Pakistan's nuclear establishment produced the unhappy example of AQ Khan, who sold nuclear weapons technology to Libya, North Korea and Iran.
He is said to have acted from a combination of ideological and financial motives.
The chance currently is less of a complete collapse of order, the kind of circumstance under which possible secret plans of yesteryear would have come into play, but of one or more individuals working inside the system providing Islamic militants with nuclear materials or, sum of all nightmares, an entire atomic weapon.