David Cameron marks 10 years as leader of the Conservative Party on December 6.
But with the Prime Minister preoccupied by military action against the Islamic State terror group and his renegotiation of Britain's membership of the EU, any celebrations to mark the anniversary are expected to be private and low-key.
Mr Cameron is only the fourth Conservative leader to reach this milestone since the start of the 20th century, trailing behind Stanley Baldwin, Sir Winston Churchill and Margaret Thatcher.
His declaration that he will quit before the general election scheduled for 2020 means that he cannot overhaul Lady Thatcher's record, in modern times, of 15 years, nine months and 17 days.
In many ways a surprise successor to Michael Howard, Mr Cameron snatched the leadership from favourite David Davis in 2005 after dazzling activists with a no-notes speech to party conference.
Aged just 39 on his election as leader, Mr Cameron was seen as the Tories' youthful answer to Tony Blair, who could shake off the Conservatives' "nasty" image and recreate them as an optimistic and modern party in a country which was still enjoying an economic boom.
Urging Conservatives to "let sunshine win the day", he promised to lead the greenest and most family-friendly government ever, pursue "well-being" as much as economic growth and match Labour spending plans on public services while delivering tax cuts by "sharing the proceeds of growth".
But the tone of his leadership was changed irrevocably by the massive financial crash of 2007/08, as he and close ally George Osborne offered an unprecedented programme of austerity to bring the ballooning deficit under control.
After failing to achieve an overall majority in the 2010 general election, Mr Cameron surprised many Westminster-watchers by forming Britain's first coalition since the Second World War with Nick Clegg's Liberal Democrats.
His first term was marked by spending cuts, riots in English cities, the phone-hacking scandal which claimed the scalp of his adviser Andy Coulson and the slow and sometimes precarious recovery from recession.
Having urged backbenchers to stop "banging on" about Europe, he found himself forced to promise an in/out EU referendum in 2013, as the rise of Ukip unsettled Tory high command and led to the defection of two MPs.
And having determined to run a foreign policy focused on trade rather than playing the global policeman like Blair, he ended up ordering RAF planes into action in Libya in 2011, Iraq in 2014 and now Syria - the latter two missions responding to the shocking rise of the Islamic State terror group, which was not even heard of when he first took up the helm but cast its bloody shadow over his premiership.
The fight against terror and the battle for Britain's future in Europe look set to dominate the second term as Prime Minister which Mr Cameron won outright in May this year, seeing off his third Labour leader in Ed Miliband in defiance of pollsters' predictions.
If things go to plan, he may also go down in history as the PM who tamed the UK's rampant budget deficit and left the country's books in surplus.
But it must all seem a far cry from the sunny visions he dreamt of when he put himself forward as Tory leader a decade ago.