It was not the most edifying of exits. It came via an article on the very last of the comment pages of a Sunday newspaper, opposite a report on the Nigerian elections that referred to “the stuffing of ballot boxes on behalf of the ruling party” and with the author’s byline photograph directly above a Shredded Wheat advertisement. Then again, this may have been appropriate.

Gordon Brown has had the Labour leadership contest stitched up for years and if David Miliband had challenged him it would have been as a sort of Shredded Wheat alternative — pure, healthy, wholesome, natural and environmentally friendly. As it is, Mr Miliband, the Environment Secretary, finally made it absolutely clear that he would endorse the Chancellor.

A little strangely, though, he managed to publish what was in effect a manifesto while at the same time ruling himself out. This prospectus was enough in itself to demonstrate that he was not ready to launch a campaign. His testimony referred to the need to devise a “New Labour Plus” (which sounds faintly like a Viagra byproduct) and insisted that his forthcoming Climate Change Bill would “provide Britain with the world’s first eco-constitution” (does that mean it is biodegradable?). He also employed his pet division of British political history in which the Attlee era was about “I need” voters, the Thatcher epoch concerned “I want” voters and the present day is about satisfying “I can” voters (I’m afraid that reading this sort of material turns me into an “I vomit” voter).

Despite all this, having known Mr Miliband on and off for 20 years since we were at university together (he was the “Dave” at Oxford who did boring stuff like student politics, rather than joining a club that specialised in smashing up restaurants), he has always been a sane, serious and sensible type. He has made a wise decision and I hope he secures a decent promotion under Mr Brown — not least to liberate him from his current Whitehall department. It has long been the case that, if one could appoint the Chief Rabbi as Foreign Secretary, his officials would turn him into an Arabist in 20 minutes. It now seems that even the most intelligent of men needs only to be sent to the Department for the Environment for half that time and emerge as an eco-fatalist.

Mr Miliband’s withdrawal will not, however, be welcomed by the Anybody But Gordon lobby in the Parliamentary Labour Party and the media (which loathes uncontested elections). Yet he was right, and for three compelling reasons.

Firstly, he will have concluded not only that he was unlikely to win, but that at this stage he was not qualified to be Prime Minister. The latter would have, admirably, bothered him more than the former. Six years in the House of Commons, a year in the Cabinet as John Prescott’s deputy and a further 12 months as Secretary of State for Global Warming are not sufficient training for No 10. In no other aspect of life would it be suggested that the best thing to do with an emerging bright young thing would be to put him in charge of everything immediately. But this seems to have become the flavour of the month in politics. Sometimes I wonder whether Sir Alan Sugar and myself are the only people left in Britain who believe in apprenticeship.

Second, “New Labour Plus” is not really what the Labour Party or voters are looking for. It is instead “New Labour Minus” that has traction. This would retain the essence of Blairism — the combination of economic efficiency and social justice — while removing other aspects — such as the trite cult of celebrity politics, the tendency to focus on the big picture but ignore the detailed brushwork and the periodic impulse to invade other countries (which, personally, I like but no one else seems to). Mr Brown has had a monopoly on “New Labour Minus” for a lifetime. It is in his bloodstream.

Third, it is wrong to assert that Labour has to have a “genuine” battle over the Blair succession or else the party and the nation will have been swizzed in some fashion. The Conservatives elevated Michael Howard unopposed in 2003, and although they did not triumph at the polls, they were not the shambles that they would have been if Iain Duncan Smith (who won a “proper” election) had carried the Tory standard at the 2005 election. Where there is a consensus around a name, as there is in Labour for Mr Brown, outside the al-Qaeda branch of the Blairites, then there is no logic in creating a leadership race for the sake of it. This is meant to be heavyweight politics, after all, not a rip-off of Pop Idol.

So, barring the most bizarre of accidents, the Chancellor will wear the crown. The only rival who ever met the qualification test is John Reid, the Home Secretary, who has many virtues, but I cannot see the Labour Party embracing a man who appears to think that Mr Blair has been a fine Prime Minister overall but a bit of a Commie poofter on certain issues.

It is possible that Charles Clarke may run, despite denials. But it is difficult to imagine that there are 44 Labour MPs prepared to sign a de facto suicide note by nominating him, or how he would square that he was forced out of the Home Office last year over the foreign prisoners fiasco with the notion that he is the ideal chap to take command of the country. So it will be Mr Brown versus a token Trot backbench MP — or Mr Brown elected without any competition.

Mr Miliband has simply confirmed the inevitable. In the end, there was never destined to be space for the Shredded Wheat option. It will come down, as it always would do, to Scott’s porridge oats or nothing.

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