Why the U-turn over Campbell?

By Nick Assinder BBC News Online political correspondent

Campbell always wanted to give evidence

According to Downing Street, Alastair Campbell is being allowed to give evidence to the inquiry into Iraq because of inaccurate claims made in Sunday newspapers.

Mr Campbell must be allowed to set the record straight and correct the inaccuracies, said the prime minister's official spokesman.

In particular, Mr Campbell wants to correct reports that the infamous "dodgy document" was prepared for him by four individuals, three of whom worked for him.

This astonishing U-turn comes only three days after Downing Street told the Commons foreign affairs select committee that there was no way Mr Campbell could give evidence.

To do so would not only break pervious precedents but create a dangerous new one, committee chairman Donald Anderson was told.

It is now abundantly clear that, over the weekend, Tony Blair, Foreign Secretary Jack Straw and Mr Campbell have been frantically looking for an excuse to execute an about face.

Several theories

Someone came up with the idea that it would be perfectly acceptable for Mr Campbell to give evidence in his role as head of the Iraqi communications group - the Whitehall press machine set up to handle the war.

Straw and Blair found an excuse to U turn

What had never been allowable was for him to give evidence about any advice he may have given to the prime minister, or his role in Downing Street.

Most find this all pretty thin. None of the weekend allegations were particularly new and it has always been known that Mr Campbell had the role as the committee chairman.

So the question remains. Why has the prime minister suddenly decided his spin doctor should be allowed to go before the committee?

There are several theories floating around Westminster.

First is the relatively simple suggestion that the prime minister is rattled by all the claims being made about his handling of the war and, more particularly, the run-up to it.

Where he sees blatant inaccuracies, he wants them corrected before the idea that he deliberately conned parliament and the public into backing the war takes firm hold.

The dangers of putting Mr Campbell before the committee for cross examination are outweighed by the dangers of allowing the allegations to go unchallenged.

Fed up

Second there is the suggestion that the prime minister is actually pretty fed up with Mr Campbell and his alleged grumpiness about being refused an opportunity to clear his name.

He is also fed up at the regular reports - repeated in a Sunday newspaper - that Mr Campbell is about to jump ship.

He has, in effect, told Mr Campbell that, as he got the government into this mess by spinning the document in the first place, he must get it out.

The third explanation is that the reports that Mr Campbell wants out are true and he wants to clear his name before he goes.

There will undoubtedly be more theories ahead.

Meanwhile, all eyes are now on the committee session when he appears. It should be riveting stuff.