He was the leader who told his party to "stop banging on about Europe", but David Cameron will go down in history as the Prime Minister who presided over Britain's decisive break with Brussels.
When he emerged from the debris of the Tories' third successive general election defeat at the hands of Tony Blair's New Labour, Mr Cameron seemed to offer his party new hope after years in the doldrums.
But a decade on - like Margaret Thatcher and John Major before him - he has seen his premiership torn apart by the unresolved tensions within the Conservative Party over the EU.
Following his election as Tory leader in 2005, Mr Cameron quickly set about re-shaping the party in his own image - embracing causes like the environment and climate change, promoting women candidates, and promising to fix "broken Britain".
Fresh-faced and energetic, the self-proclaimed "heir to Blair" with his sunny optimistic vision for the future appeared to offer the antidote to the Conservatives' old image as the "nasty party".
And after years of internal feuding it seemed the Tories were finally ready to set aside their bitter differences over Europe and the euro, settling on a position that was yes to Britain's membership of the EU but no to single currency.
But for all his slick presentational skills and modernising zeal, when it came to the general election of 2010, Mr Cameron was unable to deliver an overall Commons majority to the intense disappointment of many of his supporters.
Instead, he was forced to enter a coalition with the Liberal Democrats and while his partnership with Nick Clegg may have delivered much-needed stability in the aftermath of the financial crisis, there was no disguising the frustration in the Tory ranks.
Many held Mr Cameron personally responsible for not pursuing a more traditional Tory agenda with a harder line on Europe. The adoption in office of policies such as same-sex marriage only heightened the divide.
At the same time, the ground was shifting within the party on Europe. The election had brought a new cohort of Eurosceptic MPs to Westminster - and suddenly the question was no longer in or out of the euro but whether Britain should be in the EU at all.
Faced with growing pressure, Mr Cameron sought to assuage his backbenchers - making good on a promise made during the leadership election to pull Tory MEPs out of the main conservative group in the European Parliament, regarded by many as too federalist.
But it was never going to be enough for the increasingly vociferous Eurosceptic lobby on the Tory benches, egged on by the meteoric rise of Ukip as it capitalised on the unpopularity of government austerity cuts to make striking gains in local council and European parliamentary elections.
In January 2013, Mr Cameron finally bowed to the clamour announcing in his Bloomberg speech that if he was re-elected in 2015 he would renegotiate the terms of Britain's EU membership and then put the outcome to voters in an in/out referendum.
It must have seemed a gamble worth taking. Polls had consistently put a solid majority in favour of continued EU membership and a victory for In would finally lance the boil in the Conservative Party and seal his legacy as the man who settled Britain's place in Europe.
In May 2015 Mr Cameron celebrated "the sweetest victory of all", as voters finally gave him the longed-for outright Commons majority which eluded him in 2010 - but the joy was short-lived.
Just 11 months later he was on the steps of Downing Street, his voice choked with emotion announcing the premature end of his time in office.
He may have hoped to be remembered as the premier who rebuilt Britain's battered economy and healed a nation's wounds, but history is likely to record he left behind a divided party and set his country on a new, uncertain course outside the EU.