David Cameron took over as Tory leader in 2005
The Conservative Party can claim to be the oldest political party in Europe.
In the 17th Century, its predecessors - the Tories - backed the power of the Crown, believing it to be a check on Parliament and the interests of their political opponents, the Whigs.
The Whigs dominated 18th Century parliaments until William Pitt the Younger became prime minister in 1783.
His support for free trade and sound finances laid the foundations of modern Conservatism. Opposition to state interference in private enterprise became one of the party's core beliefs.
In 1830, the description "conservative" was first used to label this political movement, although the term "Tory" - from the Irish Gaelic word for "bandit" or "outlaw" - has remained in common use to this day.
In the middle of the 19th Century, Conservatives were split over the decision by their prime minister, Sir Robert Peel, to abolish the Corn Laws, which had maintained the price of food at an artificially high level.
On one side were those who believed in free trade; on the other, those who wanted to protect agricultural interests.
But under the leadership of Benjamin Disraeli, the party united in support of an agenda that would strengthen Britain's position in the world, while offering improvements in conditions for the less well off.
In 1886, the Liberal Party split over the issue of home rule for Ireland, and the Liberal Unionist Party was formed. It formed an alliance with the Tories before being formally absorbed in 1912, creating the full title of the present-day organisation: the Conservative and Unionist Party.
Chamberlain failed to stand up to Hitler
Although traditionally associated with landowners and the aristocracy, and more recently the middle classes, the party has looked for support across social boundaries.
After the extension of the franchise in the 20th Century, working class votes became increasingly important to secure victory at the polls.
In the 1930s, Conservative prime ministers faced crises at home and abroad.
For Stanley Baldwin, it was the abdication of Edward VIII. For Neville Chamberlain, it was the disastrous policy of trying to appease Adolf Hitler.
When "peace in our time" turned into all-out war, Winston Churchill emerged as the man to lead the Conservatives and the country, out of the abyss.
As head of an all-party government, he epitomised Britain's determination never to surrender, and became revered as one of the Tories' greatest leaders.
This made it all the more shocking for the Conservatives to see Labour elected by a landslide at the election of 1945, after the hardships of the 1930s, the country demanded social change.
However, by 1951 the Tories were back in power and a period of prosperity helped keep them there for 13 years.
Supermac to Maggie
Prime Minister Harold Macmillan, who took over in 1957, famously told voters: "You've never had it so good."
But by 1964, the country was in recession, and the Tories had been damaged by the Profumo scandal. Britain was in the midst of Beatlemania, and Merseyside MP and Labour leader Harold Wilson became prime minister during the Swinging Sixties.
Churchill led an all-party government during World War II
Edward Heath restored Tory fortunes in 1970, but Labour returned to power in the two elections of 1974.
It took Britain's first woman prime minister - Margaret Thatcher - to begin an extraordinary period of electoral success for the Tories in 1979.
At home she took on the trade unions and began privatising many nationalised industries. The miners' strike became an emblem of the bitter divisions within Britain, but abroad, her stature grew.
The successful campaign to expel Argentine forces from the Falklands, and her "handbagging" of various European leaders, helped to forge her image as the Iron Lady.
In the end though it was the enemies within who removed her from office and John Major was elected in her place.
As prime minister, he narrowly won the Tories their fourth election victory in a row in 1992, but he found himself leading a party increasingly divided over Britain's place in Europe.
In 1995 Mr Major resigned the leadership, telling opponents within the party to "put up or shut up". He won the leadership election, but the bitterness remained.
The Conservatives were now in the grip of "sleaze". As Mr Major launched a "back to basics" campaign, the newspapers carried embarrassing revelations about a string of Tory backbenchers and ministers, whose private lives did not accord with the party's moral values.
Margaret Thatcher led the Tories to three successive election wins
Others were forced to resign over a "cash for questions" row.
When the election came in 1997, the Conservatives went down in a crushing defeat.
In the leadership election that followed, William Hague was victorious, but after failing to make any in-roads into Tony Blair's majority in 2001, he quit.
Iain Duncan Smith then took the top Tory job, but in the Commons he too failed to score against Mr Blair. By 2003, Mr Duncan Smith was out and Michael Howard was crowned party leader.
The Conservatives were defeated again in 2005 - although Labour's vote share dropped and it lost 47 seats. Michael Howard was urged to stay on as leader but quit, saying by the time of the next election he would be too old to lead a party into government.
'Green and friendly'
Into his shoes came the new - and at 39, young - David Cameron, who set about rebranding the party as greener, friendlier, and more in touch with the average Briton.
He reached out to young and female voters, and the party's poll ratings began to rise - with them consistently above Labour for the first time in more than a decade.
Former leader William Hague is now shadow foreign secretary
While Labour enjoyed a bounce in the polls when Gordon Brown replaced Tony Blair as PM in 2007 - the tables turned after Mr Brown decided against calling a snap election, following weeks of speculation.
The Conservatives accused Mr Brown of "bottling" the decision and enjoyed substantial poll leads for much of the period since.
The expenses scandal brought unwelcome stories of moats and duck houses owned by Tory grandees and Mr Cameron himself has been attacked by Labour about his privileged upbringing and Eton education but MPs of all parties had expenses embarrassments and it had little impact on the Conservatives, according to polls.
The economic crisis and recession led to a change of tone from Mr Cameron - his earlier "sunshine" appeal was replaced by a more sober outlook as he sought to persuade voters his was the party best placed to lead Britain through the recovery.
The Conservatives are hoping for a "year for change" and an end to their longest modern era period in opposition when voters go to the polls.