There is a subtle art to asking the prime minister's spokesman questions.
Some rules of thumb are very clear. Asking reshuffle questions is a complete waste of time; these are hypothetical and so easily brushed away. And queries about the state of the economy are also folly if a Budget or Pre-Budget Report is coming up.
What is slightly less clear are party political questions. The way this works in Downing Street is more than a little strange: Gordon Brown's political activities are utterly divided from his governing ones. The prime minister's spokesman speaks on behalf of the government; he is a civil servant, not a party apparatchik.
My problem is that this is damaging to No 10 - very damaging. In this afternoon's lobby briefing, for example, the prime minister's spokesman was invited to respond to Liam Fox's claims that Mr Brown was 100% wrong on his statement about the 2005 manifesto featuring promises of cuts. In fact, Dr Fox says, the Tories were seeking a £2.7 billion increase in defence spending.
This is a party political matter, we were told. So Dr Fox's criticisms went unanswered. We can of course ring up No 10 and ask to speak to the "political colleagues". But most of those in the room won't have done, and come away with a worse impression of the PM than before.
Not that they hadn't already made up their minds, of course.