ITV Leaders' Debate: When is it, who's taking part and what's the format?

Everything you need to know about tonight’s debate which will finally see Ed Miliband and David Cameron lock horns

Julie Etchingham prepares for the big night on the set of ITV Leaders' Debate 2015 (Rex Features)

Will they, won’t they, they might, hmm possibly, they are, they aren’t, they are again…the Leaders’ Debate is finally taking place tonight quashing once and for all the demands, demurs and protestations of David Cameron.

The Prime Minister will take his place alongside six other party leaders at one of the colourful podiums that wags have joked resemble ITV’s dating show Take Me Out. But instead of Paddy McGuinness shouting “no likey, no lighty”, the debate will be hosted by Julie Etchingham.

She will shepherd the politicians through the two-hour live debate and four questions, hoping to avoid what the top-heavy format is most at risk of: a bun fight with catcalls, bickering, loud interruptions and no actual answers to the questions.

Leaders’ Debate: an explainer

What is it? A seven-way debate between the leaders of the Conservative Party, the Green Party, the Liberal Democrats, the Labour Party, Plaid Cymru, the SNP and UKIP

Who’s the referee? Julie Etchingham, co-presenter of ITV News at Ten and presenter of Tonight

When and where? 8pm to 10pm, broadcast on ITV

Who? David Cameron, Natalie Bennett, Nick Clegg, Ed Miliband, Leanne Wood, Nicola Sturgeon and Nigel Farage

How will the debate work? Etchingham’s role is to “keep the debate flowing and guide it through” rather than to Jeremy Paxman the Party Leaders. She’s there to moderate and ensure the live show keeps to time and that all the contributors get their say.

Will Cameron get the best podium? Lots have been drawn to determine the podium order, and the leaders will appear on screen, left to right as follows - Natalie Bennett, Nick Clegg, Nigel Farage, Ed Miliband, Leanne Wood, Nicola Sturgeon and David Cameron.

Who will speak first? Bennett. The leaders will make short opening statements, in podium order, at the beginning of the programme and closing statements at the conclusion of the debate.

Who asks the questions? The debate will address four “substantial election questions” which have been “pre-selected” by an ITV editorial team from audience submissions. Leaders will not have seen the questions in advance.

How long will they have to answer? Each leader will give an uninterrupted one-minute answer to each question, before the debate is opened to moderated discussion between the leaders, for up to 18 minutes on each question.

Who's watching: A 200-strong specially selected audience, divided along lines of gender, age, ethnicity and social class lines to reflect the electorate.

Two hours long you say, what if the leaders need a wee? There will be one break for leaders during the two-hour live broadcast, and ITV will go to a commercial break to facilitate this.

How do we find out who won? On itv.com/news viewers will be able to "rate the debate" as they watch it, using a special interactive dial embedded on the website and social #ratethedebate.

ITV Leaders' Debate tonight from 8pm.