Ed Miliband has a knack of messing up PMQs. Most weeks he appears gawky and unsure of himself, and it makes him stumble over his words and appear overwhelmed by the habitual wall of noise from shouting Tory backbenchers.
On other occasions, like this week, he gets it right. Some of the time it works on policy issues, when the prime minister is so hopelessly exposed Miliband can run rings around him. Other times, like this week, Miliband gets personal.
When Cameron does this, he comes across like a bully. The sort of arrogant public school type who gets his way about what the starter's going to be at the Bullingdon Club annual dinner. When Miliband triumphs on personal issues, it doesn't come across like that. Often because he's mentioning the Bullingdon Club, apart from anything else.
But mostly Miliband's personal victories have a very different air to them. This week he notched one up by attacking the prime minister's 'women problem'. There are four female Conservative Cabinet ministers out of 17. That's "about a quarter", as the prime minister's spokesperson helpfully pointed out afterwards. But with Tory female MP after Tory female MP saying 'thank you, we tried this but it's not something we want to keep doing', he seems to be losing the battle of persuading women being in the Conservative parliamentary party is anything like a nice place to be.
What got Cameron on the ropes was Miliband pointing out that the government frontbench was entirely ovary-free. For some reason the four Cabinet ministers without a pinkle-punkle were absent from the Commons chamber - perhaps they can't stand the testosterone-filled barracking of the PMQs wrestling chamber. "Look at the all-male frontbench before us!" Miliband crowed. "They didn't let women into the Bullingdon Club either!"
Cameron's response was desperate. He resorted to those two usual standbys of beleaguered prime ministers: the list of Things The Government Is Doing and the statistic. Neither really got him very far. He only managed to score any kind of point when he made the simple point: "This party is proud of the fact that we had a woman prime minister!"
Playing the Thatcher card is a desperate ploy, but got the Tory backbenchers cheering. It would have worked, too, had Miliband not shot back: "Unlike him, she was a Tory leader who won general elections!"
On the screen the exclamation mark looks a bit jaunty, a bit cheeky. A bit not-that-funny. In the Commons, the tone was exactly right. Miliband followed this funny little joke of his with a quick look of glee in the Speaker's direction.
This look is worth pausing on. It's a rarely seen vision of Miliband in utter delight. It's toothy, and makes his mouth look as elastic as the Wallace and Gromit figure he's often caricatured as. It makes Miliband look very young. But not like a school bully. Like the smart alec kid at the front of a class who is not only making his teacher look very, very stupid but is also about to tie the teacher up and start a full-on riot.
Whenever Ed Miliband lets himself go in PMQs, he usually plucks up the vivacity and wittiness to best David Cameron. It doesn't happen every week. Often he lets the sheer smoothness of Cameron's political slipperiness overcome him. But when he does give himself a bit of room to take a swing at the PM, he very often becomes unstoppable.