It is somewhat disarming when a prime minister declares he does not have the information to answer a question from the leader of the opposition.
By Nick Assinder
BBC News Online political correspondent
It doesn't happen very often - prime ministers normally have an inability to accept they don't know the answer to everything.
And they are, after all, supposed to approach question time armed with defences to every conceivable grenade that could be lobbed at them.
That is why they spend so long rehearsing the event with officials beforehand.
So, when it does happen, it can be extremely dangerous. Suddenly the holder of the highest political office in the land has admitted he is fallible and has been caught out by his opponent.
It therefore takes a skilful and self-confident operator to pull it off.
But Tony Blair did just that when Michael Howard challenged him over alleged government delays to hospital treatment which could lead to eye patients losing their sight.
And the angrier the opposition leader got over what may well be a perfectly legitimate question, the calmer and more reasonable the prime minister's answers became.
He simply did not have the information to answer the question, he repeated.
He would check and, if necessary, take action. But - and here is the rub - he said previous form suggested Mr Howard may not be telling the whole story.
Now, if that is true, the prime minister will lose no time in putting him right.
If, however, Mr Howard has got it right, one can expect this issue to come back to bite Mr Blair.
Meanwhile, Liberal Democrat leader Charles Kennedy once again seized on the row over the legal basis for the Iraq war - the issue which simply will not go away.
The atmosphere "out there" he said, was that people did not believe what they were being told about it.
It was surely, therefore, in the prime minister's interests to publish that legal opinion.
He may well be right about the scepticism amongst voters "out there", but he had better not hold his breath waiting for the attorney general's advice to be published.