And so after a week punctuated by dissent and disquiet, it began. First the formalities commemorating Brussels, giving the Prime Minister a chance to do his serious face by furrowing his brow and talking slowly, taking great care to enunciate every word. In response the assembled expenses frauds, sex pests and careerists solemnly opined “hear, hear” in deep and mournful tones, with Newport MP Peter Bottomley going on to meditate profoundly on the grand themes of “hope” and “hate” in the first question of the day.

Commiserations proffered, now onwards to the heart of the matter. The Labour leader began by hitting Cameron on disability benefits, citing a letter from one Adrian of outer Timbuktu (or at least he might as well have been because Mr. Corbyn didn’t deign to expand on the whereabouts of his mysterious pen-pal). “Could the Prime Minister do what the Chancellor failed to do yesterday, and apologise to those that went through such anguish and upset during the threat of a cut in their personal independence payments?” he asked.

In a word: “no”. The Prime Minister parried the attack with a textbook Cameron response, honed on tougher opponents than his current adversary.

First he made a vague apology, deflecting the blame right back across the dispatch box the same time: “when you are faced with having to take very many very difficult decisions… as we were after becoming the Government in 2010… you do not always get every decision right”. He then followed with some dubious statistics to back up his claim: “we will continue to increase spending on disability benefits which will be £46 billion pounds by the end of this Parliament, compared to £42 billion when I became Prime Minister” (in real terms this is a decrease in funding). In fact the only part of Cameron’s textbook formula missed in his first response was the humorous parting blow, before sitting back to down to assorted “chuntering from a sedentary position” (The Speaker’s diction, not mine). Although viewers didn’t have to wait long for that.

Undeterred Jeremy pressed on, touching on homelessness and then the vast budget black hole, before finally hitting a nerve by bringing out his IDS trump card. “If it’s all so fine and dandy,” he asked, “why did the Member for Chingford feel it necessary to resign as Work and Pensions Secretary?”. Having started by sticking the knife in, Labour’s pacifist leader decided to finish by giving it a jolly good twist, innocently inquiring “isn’t the Honorable Member for Chingford right when he says this is a political decision rather than one made in the interests of people in this country”. Now Cameron’s blood was up.

On tricky ground the PM immediately knew he had to bring out the big guns. Right away he deployed lofty talk of “courage“, “responsible government” and our duties to “our children and grandchildren“. Then for the parting blow, face now flush with blood, Cameron boomed “Mr. Speaker we’ve got a very interesting document today. We’ve got the spread sheet of who is on side”, referring to Team Corbyn’s leaked loyalty list. The House erupted.

Completely in his element, Cameron went on to delineate the difference between the Corbynistas’ five categories, poking fun at Angela Eagle (“neutral but not hostile”) and Rosie Winterton (“the chief whip’s being a bit quiet because she’s in hostile”) in the process.

Continuing, he mocked the Core Support group, exclaiming to cheers from the Tory benches: “I think you can include me in that lot”. A few frontbench Labour MPs gesticulated wildly, trying to shift attention across the dispatch box at a Tory party that itself was beset by perhaps even worse divisions, but it was to little avail. Corbyn responded by inviting the Prime Minister to “leave the theatre and return to reality”, but it was similarly in vain. From that point on it was all over as Cameron proceeded to hammer Labour on the now infamous list.

Eventually of course the jibes got too much, and Bercow was forced to intervene, citing the howls of laughter and jeering as “below the dignity of the house”. A subject he knows a great deal about, having suffered all manner as devoted husband to Sally.

But like a boxer who had finally found a weak spot, Cameron pressed on, returning again and again for vicious jabs right on Corbyn’s list. Bethnal Green MP Rushanara Ali even gave into laughter herself when her question on the Chancellor’s u-turn was greeted by Cameron’s jibe that it “was good to have an intervention from someone that was neutral but not hostile”, and that if she kept going “she could join the rest of us in core group plus”. Politics as theatre should not be underestimated.

“How can he get away with this?”, some Labour MPs must have thought. Well to understand how you must first understand that this man is at the peak of his powers. Male pattern baldness? Can’t stop him. Wearing the same blue gingham shirt every day? Doesn’t matter. Party divided bitterly down the middle over Europe? Who cares. Chancellor did a whoopsie and then spent an entire day hiding under a pile of hookers and Bolivian marching powder? Meh. All Cameron needs is something to riff with and he can dismantle most opposition leaders with ease, let alone an ageing manhole enthusiast who comes to PMQs each week dressed as a poor man’s Mr. Bean.

It fell to one of the Labour MPs who had animatedly pointed back at Cameron earlier, imploring him to look at the divisions in his own party, to sum up the debate. In a hastily deleted tweet, John Woodwock proclaimed it a “F***ing disaster. Worse week for Cameron since he came in and that stupid f***ing list made us into a laughing stock”. Quite.