John Armstrong: Red faces but no senior blood spilled in leak whodunnit

So the butler did it. But not to Miss Scarlett in the conservatory with the lead piping. The deed was done by a humble messenger in the Prime Minister's Department beside the paper shredder.

As State Services Commissioner Mark Prebble observed, the final chapter of this "whodunnit" was another case of the truth being far more mundane than all the feverish speculation. However, the low-level source of this leak does not make it any less serious.

The inquiry conducted by Mr Prebble's agency reveals security procedures at the highest level of the Government to be worryingly lax.

The lapse was sufficient to justify the head of the Prime Minister's Department, Maarten Wevers, yesterday offering his resignation.

Not surprisingly, the Prime Minister did not accept it, preferring to lay all the blame for the leak of the highly-sensitive Telecom paper on the culprit, one Michael Ryan, while stressing procedures for handling confidential documents had functioned "for years and years" without a hitch.

Despite her strenuous efforts to distance herself from something that went wrong within her own department, Helen Clark has naturally been embarrassed by the proximity of the leak. However, that embarrassment is relatively low and likely to be transitory.

The breach occurred in the Prime Minister's Department, not the Prime Minister's office. The distinction is crucial. The department operates much like any non-political government department - at arm's length from its minister with its own chief executive.

The Prime Minister's office is much smaller and comprises Helen Clark's closest political advisers and press secretaries.

However, the Opposition will be relying on most people not seeing the distinction, especially when messengers routinely ferry papers between her floor of the Beehive and the department, which has offices on the floor below hers as well as in the Reserve Bank building across the road.

That was one reason why Helen Clark deliberately kept as much distance between herself and the State Services Commission inquiry, refusing progress reports and doing nothing which might suggest interference.

That was extremely wise. But Helen Clark has a sixth sense when it comes to sniffing political danger.

She would have realised that the huge flow of paper in and out of her department and the Cabinet Office increased the odds on the leak coming from that direction.

The good news for her is that it was not a minister, a minister's adviser or an official seconded to the Beehive from a government department who was responsible for the leak. That would have been far more embarrassing for Labour.

There will now be the obligatory review of security procedures. That plus the resignation offer by Mr Wevers and Helen Clark's refusal to accept it essentially close the matter.

Should Mr Wevers' head have rolled?

For all Mr Prebble's assurances about the department's procedures appearing sound, someone was able to put their hands on a confidential document, walk out of the department with it and hand it to an employee of the company most affected by its contents and recommendations.

It is astonishing that a Cabinet paper which was considered sufficiently sensitive to warrant being placed in a sealed envelope for delivery to ministers was not likewise "enveloped" when placed in a tray for shredding.

However, Mr Wevers has been an exemplary public servant who has made a huge contribution. And, in the end, even the most elaborate security systems struggle to counter human dishonesty and cunning.

Mr Prebble is right. Mr Wevers' going would serve little good purpose.