The general election of 2010 spawned the first leaders' debates and were deemed a success, as up to 10 million people tuned in to watch David Cameron, Gordon Brown and Nick Clegg do battle. The three debates some say caused the hung parliament and formed the coalition between the Conservative Party and the Liberal Democrats.

It was 'I agree with Nick' five years ago, but what phrase will be ringing around the country tonight? This is the first real debate of the election campaign, and for the first time, we will see seven party leaders battle.

They appear on prime time television to tell the nation why you should be voting for their party.

Julie Etchingham has the task of moderator for tonight's ITV debate. It will be the first time that the smaller parties will be on the same platform as the three main parties - and a chance to voice their policies to the biggest audience of their lives.

Natalie Bennett (Green Party), Nigel Farage (UKIP), Leanne Wood (Plaid Cymru) and Nicole Sturgeon (SNP) will stand side-by-side David Cameron (Conservative), Ed Miliband (Labour) and Nick Clegg (Liberal Democrats).

There will be four key questions during the two hour debate. Each leader will make a short opening and closing statement and have an uninterrupted, one-minute to answer the questions before a 'free-for-all' 18 minute debate.

Despite what is being touted by the broadcasters and some politicians, this is the only real debate between the leaders during the campaign. Prime Minister David Cameron made it clear that he would only take part in one debate, and this is it. He featured on a Question and Answer session last week, as did Ed Miliband, hosted by Channel 4 and Sky News.

With daily polls showing the chance of a hung parliament occurring again, this debate will be key to how well the smaller parties do. They could be become the king makers on 8th May as deals look set to be done. SNP leader Nicola Sturgeon, who is forecast to gain a significant number of MPs in Scotland, has promised to 'lock' David Cameron out of Downing Street, urging Miliband and Labour to do a deal with them, something which they've said no to.

The ITV Leaders' Debate airs tonight on ITV at 8pm.