Hesitation is death in Parliament. And - for once - John Key was lost for words.
Not for long, mind you. But long enough for him to momentarily look flummoxed and then seemingly rewrite the centuries-old Westminster convention that Cabinet ministers are ultimately responsible for what happens in their portfolios - good or bad.
If things go really wrong, then the minister is obliged to resign even though he or she may not be to blame. Of course, this principle is one preached far more often than practised.
The new Key Doctrine would make ministerial accountability even weaker. It can be boiled down to two words: It depends.
It depends on whether a minister has actually been told by his or her officials that something is happening. That was the Prime Minister's defence following the purchase of the expensive new BMW sedans to chauffeur Cabinet ministers from here to there.
Key has pleaded ignorance of the purchase before it was too late to halt it - even though he was responsible, as the minister-in-charge of Ministerial Services.
In Parliament yesterday, Labour's Grant Robertson sought to shed more sunlight on this convenient escape clause, following news that one of the 34 vehicles will have heated rear seating just in case things get too raw for visiting ministers temperature-wise in the deep south this winter.
The Labour frontbencher tabled a Department of Internal Affairs briefing note which he said listed four occasions on which Key had signed off the department's statement of intent which had mentioned the VIP vehicle fleet would be replaced.
"Can [Key] see why ... people might expect just a little bit more responsibility than his channelling of Bart Simpson with his 'I didn't do it. No one saw me do it. It's not my car anyway' routine?"
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Key, however, contested Robertson's interpretation of the statement of intent, saying it had only declared the existing BMWs "may" be replaced.
"There was no proposal that was given to me. In relation to the add-on extras ... none of those were brought to my attention. The decisions were made by Ministerial Services, with no reference to me or any minister."
With Key stepping close to crossing the line that says he is not in control of his portfolio, Trevor Mallard, one of Robertson's Labour colleagues, asked the Prime Minister if he was actually responsible for the workings of Ministerial Services.
Key had no ready answer to that. "Yes. It depends," he finally blurted. "It depends on the circumstances. I was not responsible for this particular instance, because it was not brought to my attention, and there was no reason for it to be."
However, he added that at the point the heated seats were brought to his attention, his office had rung Ministerial Services and asked whether it was possible to remove that optional extra. The reply was that the cars had been ordered and were currently on a ship to New Zealand.
Throughout the BMW saga, Key has been behind the eight ball. It is known he is none too pleased and has carpeted officials. But it makes you wonder. Is some kind of karma operating here that has the bureaucrats unconsciously exacting revenge for National's pruning of the Wellington public service?