After a sterile campaign that has turned many people off, Britons take to the polls on Thursday in a too close to call general election that could trigger an unprecedented bout of political instability.
The vote could help decide whether Britain stays in the European Union and whether Scotland remains in Britain, as well as putting some of Westminster's biggest names out of a job.
"This is the tightest election in living memory," said Professor Philip Cowley of Nottingham University. "It will almost certainly see the biggest change in the British party system in over 100 years."
Prime Minister David Cameron's Conservatives have been virtually tied with Ed Miliband's Labour in opinion polls for months and both have fought risk-averse campaigns largely avoiding actual voters.
Cameron, 48, has shown more passion in the last 10 days of the campaign, saying he feels "pumped" and "bloody lively" after being criticised for his uninspiring style.
Miliband, 45, has exceeded expectations with a string of assured performances which challenged his reputation as a geek who struggles to connect with voters. But polls suggest neither the centre-right Conservatives nor centre-left Labour will win the election outright.
That would trigger days or even weeks of haggling as both sides fight to persuade smaller parties to support them in government.
What happens next?
Millions of Britons will cast their ballots on Thursday in polling stations including churches, primary schools, hairdressing salons and even pubs.
If one party wins more than half of the House of Commons' 650 seats, it can form a government alone and that party's leader becomes prime minister.
However, this looks like being the third election since 1929 where Britain will get a hung parliament, in which no one party has a majority.
That will bring to the fore smaller parties, who could play a key role in determining who governs Britain.
The pro-independence Scottish National Party (SNP) looks set to win most of Scotland's 59 seats, up from just six.
Although an SNP-led campaign for Scottish independence was defeated in a referendum last year, the party has seen its support surge since then under new leader Nicola Sturgeon.
The SNP is willing to back a Labour minority government but Miliband has ruled out any deal with them while not excluding accepting their support on a vote-by-vote basis.
The Conservatives claim that could hasten Scottish independence as the SNP extract concessions from Labour in return for their support.Cameron's Conservatives could again team up with the centrist Liberal Democrats, with whom they have been in a coalition government since 2010.
British Prime Minister and leader of the Conservative party David Cameron addresses workers during a UK general election campaign event at ASDA supermarket's headquarters in Leeds, northern England. (AFP Photo)
But LibDem support has plunged in the last five years and leader Nick Clegg, who led them into the coalition, could lose his seat.
Nigel Farage's UK Independence Party (UKIP) could be prepared to support the Tories but only looks set to win a few seats.
Experts say Britain will look quite different after the election depending on whether the Conservatives or Labour get in, even as a minority government.
One of the biggest campaign issues has been what to do about a budget deficit of nearly £90 billion (124 billion euros, $130 billion).
Both the main parties want to eliminate it but Labour would do so by increasing taxes on the rich, while the Conservatives want to cut welfare spending by a further £12 billion.
Paul Johnson, director of the Institute of Fiscal Studies (IFS), a research body, said there were "genuinely big differences in our view on economic and fiscal matters -- the biggest choice the British electorate has seen in a generation."
At Westminster, life in a minority government would be tough.
Even if the system of fixed-term parliaments, introduced in 2011, does curb instability, the new administration could experience difficulties in passing legislation.
Another Cameron term would have the added complication of a referendum on EU membership which he has promised by 2017 if he wins.
Cameron could also face a leadership challenge from a figure like London Mayor Boris Johnson after announcing he does not want to stay in Downing Street beyond 2020.
"Like going into jail and handing the other party the key" is how Cowley described minority government.
Britain's Prime Minister could soon be yearning for life on the outside.