By Nick Assinder
BBC News political correspondent
David Cameron has a new catchphrase: "I love it."
But during an old fashioned Punch and Judy question time (they were never going to be banished for long), the more he said it the more it became apparent he was not loving it at all.
In what was instantly branded his "Ming moment", he brought out his pre-prepared Heffalump trap and followed Winnie the Pooh's example by falling headlong into it himself.
Lib Dem interim leader Sir Menzies Campbell did it a few weeks ago by talking about the problems schools had in finding permanent headmasters to replace their interim ones.
Now it was Mr Cameron's turn as he accused the prime minister of flip flopping with his alleged cave-ins to his backbench rebels over his education reforms.
Now that is usually a perfectly serviceable and, some would argue, sustainable assault.
But coming at a time when Mr Cameron knows the prime minister is concentrating his attacks on his own programme of radically changing Tory policies, it was either high risk or downright foolhardy.
Worse still, his charge came on the day a by-election leaflet said he was in agreement with the Liberal Democrats on Iraq - a war they opposed and he supports.
The prime minister had already pulled the pin from that particular grenade and had it behind his back, waiting for a chance to lob it across the despatch box.
Even in his most vivid wish-fulfilment dreams, Mr Blair could not have pictured the Tory leader offering it to him on such a gilded plate.
Blair had his grenade ready
It was so ill-judged that it was hard not to think it was deliberate.
Was it a phrase cooked up during his pre-question time rehearsals in an attempt to pre-empt the Blair assault and take some of the heat out of it? If so it was plain daft.
Or was it a simple mistake of the sort every politician makes but which, in this atmosphere, can prove fatal?
Either way it was the first real flop (and that's being kind) of Mr Cameron's question time performances.
Meanwhile, Ming did his best to look serious, responsible and Liberal with questions about the hugely controversial police mergers. And he managed it.
But it was impossible not to be distracted from just about everything else that was going on by a strange glow emanating from somewhere just behind the prime minister.
It was Gordon Brown's smile which appears, like Halley's comet, infrequently but with dazzling effect.
What on earth could it be that is giving the Chancellor such joy. And could it in any way be linked to Tony Blair's increasingly relaxed demeanour?