Sketch: Cameron’s bluster-o-meter was off the scale

In the rarefied atmosphere of a real scandal all the faculties of British politics are magnified. Every emotion in the Commons seemed as crisp and clear as if it had been distilled from the summit of Mount Everest.

This is likely to be the last major clash between Ed Miliband and David Cameron before Thursday's local elections, and the last of an extremely long two-year opening session of this parliament. It was manna from heaven for Labour, who are keen to fan the flames of the BSkyB takeover bid scandal engulfing culture secretary Jeremy Hunt for as long as possible. Hunt's special adviser has already resigned after "inappropriate" contacts with News Corporation over the bid. The question remains whether Hunt will survive.

Ed Miliband would rather he does not. So he was especially intense this afternoon in a packed Commons chamber. He seemed convinced the PM's defence was as thin as the air on the top of Everest. Thankfully he did not adopt his usual 'very disappointed in you' tone. Ed was actually going for a form of aggression, the kind used by weedy children when they're going to stand up to the tough guy. He managed to hiss words without any sibilant sounds in them. "The prime minister is defending the indefensible," he seethed. "And he knows it!"

David Cameron was trying hard to play this one by the book. He denied a "grand bargain" with Rupert Murdoch and insisted on "natural justice", both phrases used in TV interviews yesterday. Repeating soundbites is an obvious signal that a line is being held very carefully.

The PM is on a mission:improbable, in which he seeks to reserve the right to deliver judgement on whether his culture secretary has broken the ministerial code of conduct. Miliband wants the independent adviser to be the arbiter. He cleverly accused Cameron of employing "the News of the World defence" that this was "one rogue individual working alone".

As the prime minster read out his carefully prepared answer to Miliband's urgent question, all seemed under control. But Cameron's mood slowly changed as Miliband went on the attack. By the time he finished he had transformed from a sanguine, professional politician into a mess of a man. He threw his black folder ostentatiously on to the table in front of him before leaping up to stare down at Miliband. "Weak and wrong!" he yelled, a growl of emotion in his voice, vein on his forehead fit to burst.

If you've ever had a boss who would leap up, apropos of nothing, and shout verbal abuse at you, perhaps you might appreciate that this sort of behaviour is not always the epitome of civilised discourse. Miliband didn't mind a bit, of course, as he has 250-odd backslappers behind him to make him feel better. It was Cameron who seemed the most upset as Tories behind him roared their approval. Go on, 'it 'im! 'It 'im 'ARD!

Steam was coming out of Cameron's bluster-o-meter, which always reaches dangerous levels when the PM senses he's in a vulnerable position. He blustered about Labour leaders' Christenings and pyjama parties with Murdoch and co. He protested that Miliband was utterly wrong on the ministerial code. "If you're going to make these sorts of accusations," he said, again leaning over the despatch box and slicing through the air with his hands in a double chopping motion, "get your facts right!"

Cameron has an exceptional ability to hit back, and hit back 'ard, whenever it appears he's on the ropes. Not today. He was swinging wildly, but none of his swipes were reaching their target.

Meanwhile the Cabinet minister whose future is at stake, Hunt himself, was sitting up, back straight, sandwiched between Cameron on his right and George Osborne on his left. He nodded to himself whenever any MP, of whichever political creed, demanded that he lose his job if it emerges he's done anything wrong. Only in the Commons would such earnestness be considered normal. For now, protected by Cameron's smokescreen of bluster, he remains a secretary of state.