Steve Moore is a former Chief Executive of the Big Society Network, and is currently writing his first book “Brain Boxes – a history of British think tanks”.

No one who knows David Cameron or who watched him ascend to the Party leadership, back in 2005, could have believed his motivation was to oversee a EU referendum, an austerity programme of near-historic proportions or intervene militarily against nihilistic jihadi fascists in Syria. But to paraphrase Iris Chase in Margaret Atwood’s The Blind Assassin, “he knows himself to be at the mercy of events, and he knows by now that events have no mercy.”

The 9/11 attacks and the 2008 crash –  the two ‘black swan’ events that continue to shape 21st century geo-politics  – dramatically traduced the legacies of Cameron’s two immediate predecessors. Both left Number 10 involuntarily and, if anything, their reputations have declined further since.

Who knows, perhaps Cameron will himself be caught up in a swirl of unforeseen occurrences? He has invited one such with the forthcoming EU referendum. But the odds are that will be first Prime Minister in living memory to choose the the time of his leaving.

So to his legacy.

He might be satisfied with having provided stewardship for an economic recovery, repaired the public finances, accelerated public service reforms and resolved the UK-EU relationship for a generation, but having watched the speech he delivered a week ago on Life Chances I am not so sure.

Following on from his Manchester conference speech, when he returned to the themes of social renewal, evinced when he was proclaiming his ambition to build ‘The Big Society’.  It was one of the finest of his premiership.

As the Centre-Left enter into a second decade of intellectual slumber, so Cameron’s recent speech heralded his return to the social policy fray with an exuberance seldom seen since Steve Hilton’s heyday. But this was a speech with a substance that the Big Society so plainly lacked. It was also a sure sign of his maturing as a politician, of lessons having been absorbed and of focusing on the ends not just the means.  It was a speech of a Prime Minister at the peak of his powers.

Looking back, it is obvious that the Big Society concept was a last, ultimately desultory, attempt by Hilton to exhume some of the key themes of his early modernisation work and to inject brio into the Conservative Manifesto of 2010. The early focus on decentralisation, transparency, social action that characterised the 2005–2008 years had waned in the post-crash period as dealing with the deficit became hegemonic. The Big Society proved to be both confusing electorally and an impractical concept to enact in policy alongside austerity and public service reforms.

Three aspects of the speech differed materially from those delivered under Hilton’s influence.

First, the empiricism underpinning it. It bore the emphatic imprimatur of the Centre for Social Justice. It is testimony to the influence and importance of its former Director Christian Guy, who is now advising the Prime Minister on social policy. The speech was peppered with references to seminal thinkers drawn from the fields of psychology, neuroscience and sociology, including Daniel Kahneman, Carol Dweck and Robert Putnam. CSJ insights have been fundamental to the modernisation of the Conservative Party, but this speech illuminated how its credo has now become central to Cameron’s legacy aspirations. Political relevance, policy bite and analytical rigour are the key metrics the most successful think tanks. Right now, the CSJ can reasonably claim to be the most influential think tank in Britain.

Second, the speech signalled the end of insouciant, detached, stewardship of Cameron’s first term as Prime Minister. He is gripping this suite of measures from within Number 10. In the early Coalition years, for the first time in living memory, there was no Prime Ministerial education adviser in Downing Street. He is now taking personal responsibility for his second-term education agenda in an almost Blair-like fashion.

Finally, there was statism writ large. The ‘state is not the same as society rhetoric’ suddenly feels like an age ago as interventions such as the Troubled Families programme   are extolled alongside other new public initiatives to address mental health and addiction problems and early years and parenting support. Rousing calls to citizens to step up and for society to get bigger are not going to deliver this “Life Chances” legacy and the Prime Minister knows it.

Cameron launched the Big Society at the Coin Street Community Centre in March 2010, and every member of the then Shadow Cabinet spoke on behalf of the idea later that month. With the exception of Cameron himself, the words barely passed any of their lips thereafter.

If Cameron has learned his lessons from the ephemerality of the Big Society, then Life Chances has an opportunity to become his defining legacy, and one that has the potential to transformative for the Conservative Party’s reputation. But successful enactment will requite imaginative courage, a cross-Government approach and judicious policy interventions. It will also require constant championing in the media and by Ministers based on results and impact.

With the clock ticking on his time as leader and ever sign that he is restless regarding his legacy, there is every reason to be hopeful that Cameron, during his final period as leader, will resurrect of the sunny optimism of his early days and that, finally, the full promise of the modernisation of the party will have been fulfilled.