From 1974 until 2010, General Elections were very simple.

Voters cast their ballots, either Labour or the Conservative Party won a majority and the leader of one of those parties became Prime Minister the day after the country went to the polls.

Last time, it took five days for David Cameron to be able to form a Government after coalition negotiations with the Liberal Democrats.

But this time, with the opinion polls suggestion the election will be the closest in a generation, it could take even longer.

On election night, lots of results will come in between about 3.30am and 4.30am, and it will start to become clear whether anyone is going to upset the odds and win a majority.

If that doesn’t happen and things turn out as the polls are predicting, then it could take a long time to work out who is going to be Prime Minister.

Lots of the polls have Labour and the Conservatives both finishing with between 260 and 290 seats each.

There are 650 seats up for grabs, meaning a Government needs the support of 326 MPs to run the country.

In practice, it’s likely that 323 would do it because Sinn Fein, which is predicted to win four or five constituencies, does not take up its seats.

Seats such as Oxford West and Abingdon could make the difference between whether David Cameron can govern without a coalition, rule again with the Lib Dems, or will have to leave Downing Street.

If 30 or 40 Lib Dem candidates either hang on to their seats or win back marginal constituencies, then the party might have enough MPs to form a coalition with either Ed Miliband or David Cameron.

It is thought that Lib Dem leader Nick Clegg could form another coalition with the Conservatives but his MPs might not agree, with some believed to prefer governing with Labour.

Even if the Lib Dems only win 20 seats, the party would still be sought after by the other leaders who need to edge towards that magic number of 326.

Oxfordshire voters will have a say over that, but they will have no say over what happens in Scotland.

The SNP are polling impressively and it is expected that they will win anything from 40 seats to all 59 constituencies in Scotland.

It is all-but-impossible that the SNP would support the Conservatives, but if Labour ended with upwards of 270 seats it would be very tempting for Ed Miliband to do a deal with SNP leader Nicola Sturgeon.

He has ruled this out, but his alternative is to form a minority Government and hope enough MPs from other parties will either support his policies or, at least, not vote against them.

The problem for Mr Cameron is that there are likely to be more MPs from other parties who would vote against the Conservative Party than would support it.

Apart from the possibility of the Lib Dems, the only other parties who may back a Conservative Government are UKIP, the Democratic Unionist Party (DUP) and the Ulster Unionist Party, which currently has no seats but could end up with as many as three.

The DUP has made it clear it would do a deal with the Conservatives or Labour.

Mr Miliband, on the other hand, could benefit from the support of the SNP, Plaid Cymru, the Green Party and possibly the Social Democratic and Labour Party which has three MPs in Northern Ireland.

On May 27 the Queen’s Speech is scheduled to take place. The speech sets out what a Government will do in the next year or so, and if a party or a coalition of parties wants to govern it has to get it passed through Parliament.

As a result it is likely a Government of sorts will be created by that date, but there is a lot of political horse-trading and negotiating which must happen before then.

And even if a Government is formed there is the chance the Prime Minister will try to implement his policies for a few months, become more popular with the public and then hold another election.

So no matter who finally holds the keys to Downing Street, voters could be at the polls again before the year is out.