By Nick Assinder BBC News Online political correspondent

After the last two question times, Tony Blair probably devoted much of his pre-clash rehearsal with his officials preparing to combat allegations about his role in the naming of Dr David Kelly.

All, of course, wasted. Michael Howard moved on to tuition fees.

The prime minister will undoubtedly have been expecting that as well, and he was ready with a pretty effective counter attack.

It ran along the lines of the Tories having either no policy at all, or several contradictory policies.

And it was probably one of his best performances against Mr Howard yet.

Drafting error

Mr Howard was, however, better prepared. At least to the extent that he had a copy of Labour's last election manifesto to brandish about for the cameras.

And, while the prime minister could not repeat the precise words contained in that manifesto, Mr Howard could. Surprise, surprise.

"We will not introduce top up fees and have legislated to prevent them."

Clearly, suggested Mr Howard, a drafting error had crept into the document because it must have been meant to read: "We will introduce top up fees and we will legislate to introduce them."

A small matter of the word "not", really - could happen to anyone.

Plant a seed

This is a double whammy for Mr Howard.

The aim, undoubtedly, was to suggest to observers that the prime minister had broken an election pledge and, therefore, was not to be trusted.

He did not accuse the prime minister of lying, that would have been unparliamentarily.

But next week, the prime minister's future will be on the line over not only tuition fees, but the Hutton report into the death of Dr Kelly.

And the key questions, from Mr Howard's point of view, are over Mr Blair's honesty and trustworthiness.

So, just days before that vital occasion, Mr Howard sought to plant a seed in people's minds.

Elusive weapons

The better news for the prime minister, however, was the reaction he got from his backbenchers - and even Gordon Brown - when he defended his top up fees about-face.

They appear to be overwhelmingly supportive.

The rebels may simply have kept quiet, of course, but the prime minister will take some comfort from the response he did get.

Meanwhile, Liberal Democrat leader Charles Kennedy used words from George W Bush during his State of the Union address to embarrass Mr Blair over Iraq's elusive weapons of mass destruction.

Over the months, the prime minister has changed his tack over whether Saddam had WMD, using phrases such as "weapons programmes."

Now, the president has cleared up the matter by insisting that inspectors will find "weapons of mass destruction-related programme activities".

Presumably the prime minister knows what that means, but he failed to enlighten Mr Kennedy - or anybody else - preferring to state that the weapons inspectors in Iraq were continuing to look for real weapons as well as programmes.

Because, he said, they most certainly did exist once. It is just a case of finding out what on earth happened to them.