Mr Corbyn may have a rollicking sense of humour, though I've never heard it in public. Either way, he looked slightly miffed when he announced gravely that "the Italian parliament has a measure before it" and the whole house burst out laughing.
As a nation we seem to lack self-assurance these days, but we are not yet ready to believe that we need to look to Italy for tips on tax-gathering.
This measure, if enacted, would mean that Italians could refuse to pay tax for the armed forces, but would be obliged to fork over an identical amount which would be devoted instead to "peace-building".
"British taxpayers have a right of conscience not to be in the armed forces in time of war," Mr Corbyn said. "Why shouldn't they have the same right in time of peace?"
The reason is, of course, that it wouldn't work. The treasury would use the money gained by the back door to top up the usual spending on men and guns.
It all comes from the same pot. You might as well swear that you would never breathe any molecules of air which had once been sucked in by a racist - it's all mixed up; you haven't any choice.
Still, Mr Corbyn's intervention, with its nostalgic air of earnest pre-war socialism, of scratchy socks and youth hostels, cheered us all up. Most of treasury questions was a dour argument about the single currency. The government's position on this is perfectly clear: they will wait to see which way events force them to go. They hope it will be years before this happens.
The Tory position is equally clear. They will wait 10 years, and then see which way events force them to go. They know it will be years before this happens.
Naturally Labour has decided to declare this policy "extremist". They have started referring to "the extremist Conservative party" as if it was all part of the title - "the ECP" perhaps.
Gordon Brown pointed out that of the two new recruits to the ECP's treasury frontbench team, one, Oliver Letwin, "is totally against the single currency" and another, Quentin Davies, "is totally for a single currency".
Indeed Mr Davies had said some time ago that it would be "completely crazy" and "contrary to the national interest" to throw out any idea of joining the euro. To make an irrevocable decision would be "bizarre and indefensible".
Mr Davies sat on the bench looking tremendously happy, like the boy who'd cheeked the headmaster having his best barbs read for the pleasure of the school assembly.
Sir Peter Tapsell asked rather a good question about third world debt. His point was that if we sell off tons of gold to pay the debt, the resulting price collapse would do far more damage to gold exporting countries, most of which are poor.
But he can't say it as simply as that. Instead he makes a majestic oration, a limitless tour d'horizon which makes a Gladstone speech, or Fidel Castro at a Cuban Communist party congress sound like the merest clearing of the throat.
Birds fall off trees, parents become grandparents, the polar icecaps melt, and still Sir Peter speaks on, his learning wrapped up in his erudition, swaddled in turn within his arcane knowledge.
I have no note of the chancellor's reply; as well respond to the Gettysburg address.
