Why exactly the Prime Minister lost the support of his senior Cabinet colleagues is not clear. It was probably his uncertain handling of the economic downturn and a concern about Labour's electoral prospects. What we do know is that a number of the biggest figures in the Government determined that they would go and see the leader at No 10 and tell him to make way for the Foreign Secretary. And The Times can report one further particular - when the dust settled, Clement Attlee was still Prime Minister.

As Sir Stafford Cripps discovered in 1947, it is one thing to decide to oust the occupant of No 10, quite another to make it happen. For all the speculation about Gordon Brown's position now, he remains Prime Minister. No one has made a fortune underestimating the value of incumbency, particularly of Labour leaders. And if Attlee was stubborn, Mr Brown is more so.

Yesterday, the outlines of the alternative became clearer. In a newspaper article and a press conference, David Miliband began to answer questions that have troubled even those who fancy the idea of his becoming Labour leader.

The first is this - does he really want it? Given Labour's dire political position and his own innate caution, some have argued that Mr Miliband would not pick up the crown, even if it rolled out of a bush and landed at his feet. He has now answered this definitively. He does want it, and badly enough to risk being seen as disloyal to Gordon Brown.

At yesterday's press conference Mr Miliband appeared exasperated to be pressed about the leadership. Such exasperation is surprising. He knew exactly what he was doing when he wrote an article about his vision for Labour during a leadership crises and failed to mention the current leader. And he knew exactly what he was saying when he was asked: “Would Labour be mad to get rid of its leader?” and replied merely that “the Labour Party never does mad things”.

The second question to which the Foreign Secretary attempted a reply is how he would distinguish himself from David Cameron. Just as the Tories once struggled to respond to Tony Blair, so Labour has struggled to respond to the Conservative leader. The nadir was a pitiful attack on Mr Cameron's social background. Mr Miliband's attempt represents an improvement.

He repeats Mr Brown's accusation that the Tory leader is likeable but “empty” and allies this to the charge that Mr Cameron cannot be the champion of change because “he is a conservative, not a radical”. Mr Miliband may find that this line is counter-productive and reinforces the idea that Mr Cameron is reassuring. At least, however, he is making an argument that chimes with public suspicions and plays to the public's professed desire for politicans of substance.

The final question over Mr Miliband concerns who he really is and what he stands for. From behind the usual politician's phrases, some answers peeked out. His years at Mr Blair's side have made him a reformer, but one who believes firmly in government action. His article yesterday asserts the need for “government to act as a catalyst”, describes “the political creed of the Labour Party” as “combining government action and personal freedom” and suggests that social justice and better public services are inconsistent with deregulation and lower spending. His confidence in the State is striking.

Between Mr Miliband's vision and reality stands a brooding Prime Minister, an exhausted Labour Party resistant to further reform, a bankrupt party machinery dependent on the unions, a massive fiscal deficit and a worsening economic downturn. For all the questions he raised yesterday about the possibility of Labour operating under a new leader, one stands out - how?