David Miliband was the golden boy of New Labour for so long that it began to seem inevitable he would one day lead the party.
In the first of several missed opportunities, he eventually decided to hold back from what would have been a bruising – and possibly fruitless – battle
Even after the hot favourite had the crown stunningly snatched from his grasp by his little brother and declined to join his top team, many refused to rule it out.
But it is now literally a remote prospect as one of the last remaining standard bearers of the Blairite cause takes his leave not only of Parliament, but of the country.
For more than two years since the upset in the contest to succeed Gordon Brown which convulsed family relations as much as the party, Miliband has remained on the backbenches.
Vacancies in a succession of high-profile global roles came and went – Ambassador to the US, head of the IMF – without tempting the former foreign secretary from representing South Shields.
So with Ed consistently holding the fraternal door open to a top-team return, talk at Westminster was more about which role he would bestow on him than whether the comeback was on.
All the more surprise then that he seeks to end the family feud ‘soap opera’ not by joining the cast but by rolling the credits on his once-glittering political career.
Now the theme tune being hummed by Westminster wags is that of Thunderbirds as the man dubbed ‘Brains’ heads off to join International Rescue in New York.
The nickname was bestowed on him by chief Tony Blair spin doctor Alastair Campbell for his powerful intellect and mastery of policy detail as a key adviser shaping the party’s agenda.
Parachuted into the safe seat of South Shields shortly before the 2001 election, he was a minister within a year and joined the Cabinet in 2005.
When his former mentor quit 10, Downing Street in 2007, Miliband consulted Blair over whether he should challenge Gordon Brown for the succession.
But, in the first of several missed opportunities, he eventually decided to hold back from what would have been a bruising – and possibly fruitless – battle.
His appointment as the youngest foreign secretary for 30 years reflected Brown’s determination to mend fences with the Blairites and include talent from all sides of the party. But doubts over his commitment to Brown were sparked by an article in 2008, in which he discussed the future of Labour without once mentioning the Prime Minister.
Widely perceived as disloyal, it triggered calls for his dismissal and meant all eyes were on him at the subsequent party conference in Manchester. He appeared to revel in the attention, memorably posing for pictures with a banana.
But he did not mount a challenge, using his conference speech instead to hail Brown’s leadership – sparking the first of a spate of accusations of “bottling it”.
When his close friend James Purnell quit the Cabinet in June 2009 and at a subsequent attempted putsch, he held back from a resignation which could have given rebellion’s deadly momentum.
How he may have rued those missed opportunities when Ed, four years his junior and who followed closely in his career footsteps, harnessed the voting power of the unions to overtake him.
Their parents were Marxist historian Ralph Miliband and his academic wife Marion and David went to comprehensive schools in London and Leeds.
He studied politics, philosophy and economics at Corpus Christi College, Oxford, and in 1988 won a Kennedy Scholarship for a master’s degree at the Massachusetts Institute of Technology.
Miliband worked for the centre-left IPPR think tank before becoming secretary of Labour leader John Smith’s Commission on Social Justice, looking at welfare policy. From 1994 to 1997 he was Blair’s head of policy in opposition and headed the Number 10 Policy Unit throughout Labour’s first term after the 1997 landslide.
He is married to American violinist Louise Shackelton and the couple have two sons – Isaac and Jacob – adopted from her native US after years of unsuccessful IVF treatment.
Although he is an Arsenal fan, Miliband was in 2011 appointed as non-executive vice chairman of Sunderland Football Club.