The vast majority of politicians make poor newspaper commentators. This is because they usually start from a wish to advance some agenda of their own, rather than from trying to interest the reader. Many of the best professional commentators will say they don't know what they think about something until they've written it. "I'll do the Tories this week and see where it takes me," Alan Watkins used to say when I was his editor. Politicians, by contrast, are trained to avoid spontaneity and lateral thinking. Their writing carries no sense of a journey. There is rarely any point reading to the end of a politician's article; you know exactly where he or she is going to end up. In all probability, it has not been written by the politician at all, but by some hapless aide.

I am therefore surprised that the Sun has signed David Blunkett as a weekly columnist. As an editor, I avoided publishing politicians and, as a reader, I avoid reading them. I confess that I tried to woo the late Robin Cook after his resignation over the Iraq war. At that moment, he was articulating, more effectively than anyone else, the feelings of half the country. Moreover, as some of his columns read at his memorial service this month reminded us, Cook could write wittily and incisively. But even he was not always gripping reading, particularly once he had exhausted his insights on Iraq. He was, it seemed to me, struggling for fresh and surprising ideas.

There are other exceptions to my rule. Michael Foot and Boris Johnson are the most obvious living examples, but both were successful journalists before they became politicians. Foot chose to progress to a front-rank political career and his journalism suffered as he did so.

Johnson has kept both balls in the air longer than anyone else, but may have been forced to drop one of them even before you read this.

Though their semi-celebrity status gives them a head start, politicians rarely make a successful transition in the opposite direction. Matthew Parris's writing can be entrancing and his ideas quite startling. But he was only a marginal back-bench MP and admits he had no real talent for politics. George Walden, who did get to under-secretary level, is one of the cleverest and boldest thinkers around, but is best on cultural and geopolitical issues, and now wisely avoids policy and party politics. Michael Portillo, too, is best on the arts and gets by mainly on his elegant writing style.

Again, Roy Hattersley, who wins all prizes for productivity, is less interesting on politics than on almost anything else. None of those writers still sits in the Commons.

William Hague does. His weekly column in the News of the World was (now axed) banal and bland. "Keep completely calm," he advises the next Tory leader in a recent article, alongside entirely unoriginal soundbites on pensions, muggers, teaching methods and Tube strikes.

Can Blunkett cut the mustard? The Sun put his column on page 20 with minimal fanfare, which hardly suggests confidence in its new property.

Perhaps Blunkett can emulate Ann Widdecombe who, against all the odds, succeeds in newspapers because her quaint personality comes across directly and, combined with a dry wit and an instinct for punchlines, makes for a strangely compulsive read. Perhaps, in the Yorkshire bluntness stakes, he can even rival the Daily Mirror's Paul Routledge.

Blunkett's first column berated "a mawkish nation" for "pouring out . . . emotion over George Best". It went on to argue that "the real heroes" are those who don't succumb to alcohol addiction or other misfortunes but "fight back up from the bottom" and "just get on with it". Quite right, in my view. But it had been said before, and better.

Two weeks ago, I wrote that, despite the swelling applause for the Berliner-style Guardian, the new, shrunken g2 was a critical failure.

I am delighted to see that, as predicted, Ian Katz, the section editor, has introduced changes. Back are the old-style covers, as good and as inviting as ever. One, which had me turning eagerly to an article about actuaries (yes, honestly), was a fine example of the quirky intelligence that always made the section distinctive.

Inside, g2 has rediscovered its coherence and impact. Katz was thought by some to have blown his chances of eventually succeeding Alan Rusbridger as editor; but the Scott Trust will surely smile on a man who so quickly puts right his mistakes.

If the new Guardian succeeds, it is hard to see what market remains for Stephen Glover's proposed upmarket, celeb-less paper, the World.

This mysterious project has already exceeded the gestation period for a whale and will soon overtake that for an elephant. But I am happy to accept a personal assurance from Glover, my former boss at the Independent on Sunday, that it remains a runner. Even if it never launches, but keeps the Guardian honest merely by threatening to do so, we should all be grateful.