Alistair Darling reminded me of a teenager asking for money as he tried to explain why he needed yet more cash for the banks. First he told us what an incredible success his first two bank bailouts had been. Yes it had cost a few pounds — well, OK, zillions — but what a bargain it had been. We have saved the world and “fears of a worldwide depression have receded”.

It was a blag-a-thon. If Mr Darling had been a teenager, at this point his parents would have asked sharply why, if it was all going so well, he was standing there asking for yet more. But Boy Darling, age 55 and three-quarters, wouldn’t say. Instead, he bragged that his bailout of Lloyds and RBS had been so successful that he wanted to give them billions more. RBS was the real star, of course. He’d lent them £25.5 billion in February and things were so marvellous he was lending them £8 billion more. And, oh yes, to reward them further he was giving them a tax break of £9 billion to £11 billion. As you do!

What WAS he on about? The figures whizzed round us like snow in a white-out blizzard. Through the storm, I could hear the muffled sound of parents shouting: “How much do you want!?!” Boy Darling ignored them. “This revised deal is better structured, with better risk sharing and greater incentives to exit,” he bragged in a drone more deadly than a tarantula’s sting.

Then a real teenager, Georgie Boy Osborne, pointed a long bony finger at his foe. “Isn’t the real story the sheer size of this bailout?” he sneered, for that is what he is good at. “You couldn’t bring yourself to actually give us the figure in the House of Commons — £39.2 billion! Equivalent to £2,000 per family. Bigger even than the bailout last autumn.”

Boy Darling looked ahead stonily. It is very irritating when no one realises how brilliant you’ve been. I must admit that I could see his point: the entire annual budget of the Ministry of Defence is about £32 billion. This year it had cost more to save the banks than to fight a war. It was impressive, in an awful way.

The Chamber breathed a sigh of relief when Vince Cable was called. Finally, an actual grown-up! Indeed, on these matters, Vince is possibly the wisest man in the Chamber. (Admittedly, this isn’t saying much.) He stood, his trouser legs hoiked up over his ankles, as if he were wearing bicycle clips, hands clasped, voice utterly despairing.

“Can I just check the facts?” he asked, ticking off the billions in a truly frightening way. But, it seemed, that it added up to more than £39.2 billion. Later £45 billion was bandied about. This was Monopoly money territory.

Father Vince turned his attention to the new bonus regime that Boy Darling had told us was the toughest in the world because it was deferred. “Can you explain, in simple terms, why state-sponsored banks are paying bonuses at all?” said Vince, scathingly. “A bonus is surely a bonus whether it’s paid now or in three years’ time.” It meant only, he said, that bankers had to wait three years for their Ferraris?

Vrrooom vrooom. It’s the kind of question that grown-ups ask. And that teenagers duck. Boy Darling stammered that he thought bonuses handy for rewarding good behaviour. At this, Vince looked even more disgusted, if that was possible.

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