Timing is everything, Boris Johnson, as David Miliband will testify

According to the great Shakespearean critic, A C Bradley, Hamlet’s “tragic flaw” is a melancholy that prevents him from taking action. Miliband’s flaw also involved procrastination, but it reflected fastidious caution rather than melancholy. He refused to strike unless the circumstances were perfect and the risk minimal. But such a context almost never prevails in politics. His moment of opportunity was bracketed by Tony Blair’s departure in 2007 and early 2010 when a change of leader ceased to be a practical option.

Once Gordon Brown had departed, his moment had passed; the spot was no longer sweet, the window no longer wide open. Although Ed Miliband now vehemently denies doing so, David still maintains that his younger brother told him not to challenge Brown in 2009 because his “time would come”.

As it turned out, Ed was really plotting the advent of his own “time” and fought a brilliantly effective leadership campaign in 2010, aimed squarely at his brother’s perceived weaknesses – his technocratic manner (“Ed speaks human”) and his association with Blair. The younger brother’s cunning plan was to keep David out of the ring until the rules of the game had changed (to Ed’s benefit).

Does Miliband Snr’s departure matter? Yes, to the extent that he was one of the dwindling number of Labour politicians who understand that the centre ground – or common ground, if you prefer – does not shift as dramatically as politicians like to imagine. He was never an identikit Blairite, but he shared Blair’s belief that the public’s desire for economic competence, social decency, law and order and an aspirational culture is fairly constant and rarely submits to ideological lurches. Ed’s great error is to imagine that the centre ground has shifted Leftwards.

As David Miliband’s moment passes, Boris’s begins. The Mayor’s bruising interview with Eddie Mair was like watching a friendly English sheepdog rush up for a pat only for it to be smacked squarely across the chops. None of the charges was new. The interview will not have scratched Boris’s popularity, let alone dented it. But Mair’s summary condemnation – “You’re a nasty piece of work, aren’t you?” – was like a whisper of words from the future, filtered back into the studio through some wormhole in space-time. For if Boris does become Tory leader or prime minister, he will look back upon the Mair mauling as a mild warm-up, a light round of sparring before the Main Event.

In this sense, the interview was simply a punctuation mark in the Boris saga. If he is to achieve his ambition, he must be seen by his own party to be able to handle such hostile cross-examination (which he is, when prepared). He must also be seen to be in the game.

I am not one of those who thinks that David Cameron remotely deserves to be replaced before the election, or that his premiership has been an unmitigated disaster. However, there are some who cling to this extreme position and believe that a snap change of Tory leadership could save the party from defeat in 2015. Their opinions will have been hardened by last week’s YouGov poll suggesting that, with Boris at the helm, the Tories might win 40-50 seats more than under the current management.

It is less than a year since the Mayor was re-elected. For him to seek a Commons seat in the next winnable by-election would be ill-received by Londoners, and hard to explain except as a preparation for treachery. But to put himself forward for a seat in the 2015 general election would be a different matter entirely. Boris could argue quite reasonably that he hoped to assist his party on the national stage when his second term expires in 2016. Yes, he would be performing two roles – Mayor and constituency MP – for a year. But there is recent precedent in Ken Livingstone, who served as Mayor and as MP for Brent East for just over a year before the 2001 general election.

If Cameron defies the Tory soothsayers and wins in 2015, Boris’s chances of succeeding him will diminish dramatically. As the PM revealed in a Sunday Telegraph interview in January, he would like to go on until at least 2020. Thereafter, the younger generation – especially the 2010 intake – will be staking their claim and seeking to assert their identity as a cohort. By 2020, the London Olympics, the greatest leadership campaign launch in history, will be a cherished but distant memory.

This is why it was so important for Boris to say explicitly what we all know to be true: that he wants the job. You don’t have to support him to see that, somehow or other, he must be a candidate in the next leadership contest. On his side is prodigious talent and popularity. Against him – a sceptical Tory oligarchy, and the intrinsic difficulty of matching ambition and political context. But he has at least declared himself. As the Dane says: the readiness is all.