The Sketch: After all the laughter, the joke's on Dave

When I was a naked little boy, my big sister took me into the bathroom with the words, "Let's play a game." The game was "lifting each other into the bath". She lifted me in and let me go. I yelped, I screamed, I suffered. Readers, it was winter and she had filled the bath from the cold tap. When I had struggled out I said, "Right, it's my turn now," and she said, "We're not playing that game now."

David Cameron has spent years tormenting the Prime Minister with cruel jokes. Now that Gordon has replied with two or three jokes of his own, Cameron has said, "We're not playing that game now."

Yesterday, he kept his remarks very tightly held in a ring of dead soldiers, crushed Haitians and tortured schoolboys. Not quite fair of him (and you know what a champion of fairness the Sketch is). All that carnage. No room there to play the game. No opportunity for Labour backbenchers to rock to and fro and "roar with laughter" (technical term).

Brown had to make do with feed lines planted in his back benches. Emily Thornberry surprised us all by offering herself as the Ball to the prime ministerial Cannon. She said something about a marriage tax break to encourage her constituents to "tie the knot" and Brown shot back: "It is the Conservative Party that is in a knot." But we weren't playing that game.

But truth to tell, it did sound as if we were. This is a serious limitation in Cameron. He's only got one tone of voice for everything he does. It's the same slightly strained, yearning, pleading voice – with his right hand tapping the despatch box for emphasis, fingers splayed to show he really means it.

Tony Blair was always defeated by William Hague in the Commons until Blair decided, "We're not playing that game now." The game had been Duelling Tenors – and quite suddenly, one day Blair started speaking normally. "We all like the honourable gentleman's jokes, he said, "they're very funny, but..."

And at a stroke, Hague's brilliant artistry looked artificial. It was devastating, at the time. Cameron needs to do something like this to Brown, or Brown will do something like this to him.

NB: One point did come up. Brown said that the Government would support the creation of a backbench business committee. Such a thing is a major innovation. It would take significant powers away from the Government (to clog up the schedule with their junk legislation, for one thing). And there, he said the Government would support the parliamentary election of committee members and a business committee.

How's he going to get out of that? There's absolutely no way he can allow it to happen. I will eat the most disgusting tasting hat you can send me if he does.

simoncarr@sketch.sc