But there is a risk that the Leeds-raised Foreign Secretary is being too clever by half with his unofficial campaign for Labour's leadership that was, effectively, launched a fortnight ago with an article calling on the Party to stop feeling sorry for itself, and even more so given his subsequent near-silence on the gravity of the stand-off between Russia and Georgia.

And the problem is this. By placing his head above the parapet – and then doing absolutely nothing to quell reports that he wants to usurp the Prime Minister – the debonair Miliband is in danger of becoming such a divisive figure that he will never become his party's leader, whether it be this autumn or at a time of Gordon Brown's choosing.

If he wanted the leadership, he should have said so publicly – and without equivocation. For, if he had done so, there is every prospect that Brown's summer sojourn in Suffolk might have become an extended holiday, and Miliband could be measuring up 10 Downing Street for new curtains. Brown's political execution needed to have been short and brutal.

Instead, Miliband faces the prospect of returning from his own holiday, in Spain, to find the knives out for him and Brown contemplating whether to cut the young upstart down to size by rewarding such disloyalty with, arguably, the toughest job in the Government; responsibility for the nation's finances as Chancellor of the Exchequer.

In many respects, this might suit Brown – and the country. By removing the unconvincing Alistair Darling from the Treasury, it would ease the Scottish-bias in the Government's upper echelons.

It would also remind the one-time pupil of Benton Park Secondary School that it is policies – and not personalities – that still matter most of all.

And it would also leave Miliband with little scope to plot his own future; he would be too pre-occupied with trying to devise a new economic strategy.

For it appears, in many respects, that Miliband has had too much thinking time in recent months – despite his supposed onerous responsibilities as Foreign Secretary at a time when so many members of the Armed Forces are heroically sacrificing their lives in Iraq and Afghanistan and when Russia has been reasserting its authority.

Like hosting a special dinner at the Foreign Office where one of the guests was none other than David Abrahams – a reclusive businessman and leading Labour donor.

Like his radio interviews that followed his now infamous Guardian article when his support for Brown was lukewarm at best.

Like allowing himself to be photographed in the street buying a pint of milk while dressed in casual attire; timed, no doubt, to contrast with Brown's unease in front of the cameras prior to his Suffolk holiday.

Like informing the Press that he would not be visiting India early next month – presumably because of the more pressing nature of domestic politics – rather than having the courtesy to first inform diplomats at the Indian High Commission.

Like allowing his staff to intimate that Alan Milburn, the immensely unpopular and divisive former Health Secretary, could be Chancellor in a future Miliband government before denying this report. As veteran Labour backbencher Peter Kilfoyle recanted so cuttingly: "Apart from the obvious fact that there is no vacancy, it will reinforce the view that Mr Miliband is a political lightweight, lacking the experience to make informed and acceptable political judgments."

And like Miliband's final posting on his Foreign Office blog before departing for the Mediterranean: "Blog resumes in three weeks or so. Hopefully browner and fresher."

Browner? Is this the conduct of an aspiring Prime Minister?

No.

If Miliband wanted to demonstrate his leadership qualities, he would have cut short his own holiday and embarked upon a round of shuttle diplomacy to bring about an immediate ceasefire in Georgia before even more lives are lost. Instead, his lack of intervention strengthens the belief that Miliband, and his associates, are pre-occupied with their plotting against Gordon Brown.

It is now clear that Team Miliband is waiting for the prospect of a politician, or group of Cabinet ministers, to have the courage to put the PM out of his misery before they step into the breach. They are clearly banking on this happening sooner rather than later.

They should caution, however, against such a presumptuous strategy by studying the rise and fall of another political heir apparent who once held lofty ambitions above his station – one Michael Denzil Xavier Portillo.

A devotee of Margaret Thatcher, the then Employment Secretary let it be known throughout 1995, when John Major's government was at its nadir, that he wanted to replace the PM. He did nothing to dampen speculation.

But, when Major chose to call the bluff of his opponents by hastily convening a "back me or sack me" leadership contest, Portillo lost his bottle – even though his campaign team were in place and had installed additional telephone lines at their supposed HQ. It was left to John Redwood, an uninspiring intellectual, to oppose the then Prime Minister.

Portillo's strategy was clear. He assumed he would become leader after the Tories lost the 1997 election. However, he made one fatal calculation. He failed to assess the vulnerability of his Enfield Southgate seat to a Labour landslide.

When I interviewed Portillo, the then Defence Secretary, in Nottingham two days before Tony Blair swept to power, I asked him teasingly about his base camp – and whether he would retain the seat.

"No need to worry," said Portillo with typical arrogance. How wrong could you get. His defeat was a defining moment of election night.

But, more fundamentally, Portillo's disloyalty ensured that he had too many enemies when he was eventually in a position to stand for the Tory leadership in 2001 following William Hague's resignation.

It is a lesson from history that David Miliband should weigh up. Having been so closely associated with the Blair years, and so openly hostile to Brown, it will be virtually impossible for him to unite the Labour Party – despite his charm and confidence in front of the cameras. But, on the other hand, his prospects may be even bleaker after the next election when Labour's ranks may be dominated by left-of-centre MPs who are unlikely to be natural supporters of Miliband.

That is the dilemma facing David Miliband as Labour's most crucial party conference for years draws nearer. For, by revealing his hand so early, and then failing to adequately respond to the new foreign policy threat posed by a resurgent Russia, he may find himself out of leadership contention before a contest has even been called. And he will only have himself to blame.