Nick Clegg and Nigel Farage are tonight making their final preparations ahead of a televised showdown over Britain's place in the European Union.
The Deputy Prime Minister and Ukip leader will fight to win over the public tomorrow in the first of two debates between "the party of in and the party of out" being staged in the run-up to the European Parliament elections in May.
Mr Farage's performance in the clash, which will be broadcast from 7pm on LBC and Sky News, will be intensely scrutinised in Westminster where Ukip's growing popularity is causing jitters among the main parties.
A Lib Dem source played down expectations ahead of the debate, telling reporters : "He's the Deputy Prime Minister, he has a pretty busy day job - preparation time has been fairly limited.
"We are preparing as we would for any major event in the diary, making sure we are across all the facts and figures on Europe as it's not something he's been involved in at a granular level every single day.
"We are doing it as and when we can."
Asked if civil servants have helped with the preparations, the source added: "We have staff at headquarters that are able to provide lots of information.
"We have had special advisers working on it... Obviously there is lots of information available on Europe that exists in government.
"Nick is the DPM and in the debate he's very likely to be asked about Government policy."
Echoing the 2010 general election leaders' debates, the arrangements agreed for the head-to-head have been tightly controlled.
The audience has been selected to reflect the UK population as well as a spread of views on the EU debate.
Questions will be screened by an editorial panel but the parties will not see them in advance.
The party leaders will both make opening and closing statements and will have one minute to answer questions from the audience before presenter Nick Ferrari opens up the subjects to free debate.
Mr Farage is a Ukip MEP for the South East of England and was re-elected party leader in November 2010 after a brief spell away from the helm.
He said he had "no choice" but to pick up the gauntlet thrown down by the Deputy Prime Minister to thrash out the arguments in a live broadcast as there had been no "full national debate" on Britain's membership of the EU for many years.
Mr Clegg, a former East Midlands MEP who speaks French, German, Spanish and Dutch, has said he wants to dispel the "myths" being peddled by "isolationists" and levelled a personal attack at the Ukip leader, accusing him of pocketing his MEP's salary but not bothering to vote.
The second debate will be broadcast on BBC2 on April 2 and will also be broadcast by Sky News.
In an article on The Independent's website Mr Farage said he had been " waiting years for this opportunity" and insisted he "won't be wasting it".
He wrote: " There was no way I was going to turn down the opportunity to debate with the Deputy Prime Minister ahead of the European elections.
"Wednesday night's event is something I've been wanting to happen for years; the bigger surprise is that Mr Clegg took up the challenge.
"But then his party is facing the prospect of electoral wipe-out at these elections unless they do something drastic. For them, it's about survival. There is no reason why any establishment party would otherwise want to highlight the huge number of competences which Brussels now has over our lives - especially on a live broadcast and televised debate."
He added: " My position is clear, and we have the clear, pragmatic business argument on our side. A few multinationals love the EU because it drives out competition with the costs of compliance and regulation. But the backbone of this country - small and medium-sized businesses - are the ones who are looking towards Ukip's policy.
" But what does Nick Clegg want? And will he tell the country in these debates what reforms he thinks are needed? Or will we still be left guessing what their policy is aside from a desire to cling to an undemocratic and inefficient mode of government?"