The Milibands, the Jacob and Esau of politics, go their separate ways

You chose the wrong night to resign - that was a my initial,  cynical, reaction when news broke that David Miliband is to step down as a Labour MP.

If David Miliband shared the streak of ruthlessness his brother Ed demonstrated in standing against him for the leadership, he would have walked out on another night -  in June 2009 - when his friend James Purnell called the game on Gordon Brown.

Because he stayed loyal to the cabinet the Purnell rebellion that would have decapitated Gordon Brown and installed one David Miliband as leader never happened.

Instead the inevitable happened, and Labour went down to one of the most crushing defeats in its history because MPs allowed their loyalty to get the better of them, and were bullied and shackled to a flawed leader.

Not all, of course. An honourable exception was the late David Cairns MP, who was sacked from the government for uttering criticism of Brown's leadership style.

When David Miliband spoke at a memorial fundraiser for Cairn's charity a few years ago he was mesmerising. Defeat by his brother,  and a spell in the political wilderness, seemed to have done wonders for him.

He made an incredible speech at the event -  witty, warm, visionary and full of political potential.  People were left in tears, particularly those who had that day witnessed a flat-footed performance by his brother at Prime Minister's Questions.

But Ed Miliband has improved since then,  and the parliamentary Labour party remains remarkably united. But there was always the question of David hanging over the family.

Whenever he spoke in the Commons, or made any intervention, it raised the question of whether he would come back into the shadow cabinet, if the room was big enough for both brothers, and what the implications would be for everyone else in the court.

Had David joined the shadow cabinet we would hardly have written another word about David Cameron and Nick Clegg between now and 2015. The focus would be on the Jacob and Esau of British politics, one born clutching the heel of the other's ambition. It would have been intolerable for both, but it would have made incredible politics, and a combination that would have vanquished the Coalition.

Ed Miliband made an open door offer to his brother, but those who know them said they were not reconciled, which is the greatest tragedy of this saga. I have a brother, so I know how brothers wound each other, but the greater pain is not being able to recover from the fall out.  

Before he is even gone there is talk of a David Miliband comeback. But almost all the Blairites have gone now, and few in Labour will see him as a Prince o'er the water, waiting to come and claim the crown. The Tories of course will try to keep his shadow alive as much as they can,  an ocean of safety now between them and the danger he posed.

Labour is a tribe as much as a party, and if David Miliband is not engaged in the election of 2015, and Labour do not win, then the party will not take kindly to him waltzing back in without blood or a battlescar on his tunic. British politics, by then, will have moved on

For every man there is a season, a time for every purpose. If David Miliband harbours any bitterness about not being Labour leader it should go back to his own failure to recognise, on that night in 2009, that it was time for action.