Looking troubled, he failed to come up with answers

Usually Tony Blair presides over his monthly news conferences with authoritative aplomb. For more than two years he has never looked remotely troubled during the question-and-answer sessions. But there was always going to be an occasion when his scheduled news conference coincided with the sudden eruption of a potentially big, awkward and embarrassing story. Yesterday such a story erupted. Mr Blair looked troubled.

Probably he would have coped stoically if he had faced questions about one difficult story. He was well prepared to deal with the collapse of the case against Katharine Gun, the GCHQ worker who had leaked an e-mail about an Anglo-American operation to eavesdrop on the UN Security Council: "There was no political interference ... we will obviously reflect on the implications."

On BBC Radio 4's Today programme a few hours earlier, Ms Short put rockets on the story, to revive a phrase Mr Blair deploys from time to time. Objectively the surprise is that anyone is surprised that intelligence services might have targeted the UN. This is the sort of activity they tend to engage in a lot of the time. But objectivity does not come into it. Ms Short shone some light on a specific operation that she claimed took place, not against a bunch of terrorists, but on the saintly Kofi Annan.

This would take some answering, and Mr Blair could not come up with any answers at all. As he acknowledged, Ms Short had placed him in an impossible position. Prime ministers, he insisted, did not comment on intelligence matters.

He stressed that this unavoidable evasiveness should not be taken as an admission of guilt, but his inquisitors were restless. For the first time since Downing Street instigated the news conferences, some of the exchanges became mini interviews. Mr Blair stressed his admiration for the intelligence services and his disapproval of the "irresponsible" Ms Short. But even when journalists moved on to Mr Blair's chosen terrain, the behaviour of Ms Short, he did not have the answers. He was asked how he planned to punish Ms Short. Mr Blair said that he needed more time to reflect on the fate of his former cabinet colleague. I suspect that on reflection, Mr Blair will not dare to do very much. This is not a moment to turn his tormentor into a political martyr. Mr Blair was not in a strong enough position to sack her from the Cabinet. He has little room for manoeuvre now she is a backbencher.

The waves from the specific story will subside, but this should be of limited comfort for the Prime Minister.

He sought yesterday to highlight a new initiative on Africa and policies aimed at addressing anti-social behaviour in Britain.

But he was asked only two questions on Africa and none on anti-social behaviour. This should worry him more than the precise details of Ms Short's claims. He is still justifying the war against Iraq and cannot move on from it.