Dawn Primarolo repeated the news for the coach parties in the upper circle and the audience sagged a little - no point cancelling the babysitter now, but it was a blow all the same. It wasn't Hamlet without the Prince exactly, more Pinocchio without the puppet, since Mr Brown's big attraction for Conservative backbenchers is his glowering determination not to tell the truth about the tax burden.
In committee the other day, Michael Fallon and several of his colleagues had pushed this reluctance to the point of surreal comedy, and Tories had come for more of the same. They got it, though it lacks a little savour without Mr Brown's ferocious deadpan at centre stage. When he is questioned on such matters, he looks back at his persecutors with a level stare which can best be translated as: "I've got to behave now, but if I ever meet you down a dark alley I'll shove your fiscal statistics somewhere the National Audit Office won't find them."
Three MPs had taken up Mr Fallon's cudgel, their questions similar enough for Mr Smith to take them in one go. We had already had a warm-up act - Dawn Primarolo having been asked why the Government had shown Working Family Tax Credit in the national budget rather than as public spending.
But this was just preliminary stretching. The real issue is whether the Government can somehow be forced to admit that the tax burden is higher than it was when they took office. There isn't much doubt about this. Labour ministers know it to be true, as do their Conservative opponents. But they would rather die than say it.
The chief tactic is the surreptitious verbal shimmy, reminiscent of a pavement shell game. Tories ask whether the tax burden now is higher than it was when Labour came to office and their Labour counterparts wearily answer that the tax burden is falling not rising.
In other words, they answer an inquiry about the future rather than the past. But no one is fooled. Even a seven-year-old could work it out, given the frequency with which it is played out. No one is missing the point either, though we are repeatedly told they are, and no one is, strictly speaking, telling a lie.
Tories are capable of similar grammatical sleight of hand, of course - we were told at one point yesterday that the Prime Minister had confirmed the tax burden was rising, something I don't think Mr Blair would do even if he were to have slivers of bamboo pushed beneath his fingernails.
A qualified concession about past circumstances had been turned into an astonishing confession about a continuing state of affairs. But the Tories don't stand to lose as much as the Government do by persisting with this stand-off. A government with a large majority and a solid lead in the polls which chooses to look evasive and duplicitous because it cannot bear to acknowledge a mildly uncomfortable fact is a dismal spectacle.
Yes, the Conservatives would crow if they ever did say it, but that crowing would become stale far more quickly than their unanswered questions. Mr Blair dismissed the Conservative fixation on this issue as being "just a game" the other day, but the truth is that the game only continues because Labour are so hysterically determined not to lose it.