With David Cameron still away in the US, it was Nick Clegg who manned the dispatch box at today's PMQs, but rather than targeting Clegg, Harriet Harman (who, as is traditional when Cameron is absent, replaced Ed Miliband) chose to concentrate her fire on Cameron. "Why is it that out of the last eight Wednesdays, the Prime Minister has only answered questions in this House once?", she asked. It was a strong stat, and Harman followed it up with another fine line: "He's been busy explaining to President Obama the benefits of Britain's membership of the EU, why is he able to do it in the White House but not in this House?" She went on to ridicule Cameron's dithering over the Queen's Speech EU amendment: "if the Prime Minister was here, would he be voting for the government, against the government or showing true leadership and abstaining?"
In response, a loyal Clegg resisted the temptation to have fun at Cameron's expense and turned his guns on the absent Miliband, declaring that it was the Labour leader "who should be relieved that there isn't Prime Minister's Questions". Referring to Miliband's recent disastrous World At One interview, he quipped: "he denied that borrowing would go up under Labour's plans 10 times, who said that there isn't enough comedy on Radio 4?"
As I predicted earlier , Tory MPs seized the opportunity to remind Clegg of his past support for a vote on EU membership, with two brandishing the 2008 Lib Dem leaflet calling for "a real referendum". In response, Clegg insisted that his position had not changed; he supports a referendum the next time that there is a formal change in Britain's relationship with the EU (the 2010 Lib Dem manifesto stated: "The European Union has evolved significantly since the last public vote on membership over thirty years ago. Liberal Democrats therefore remain committed to an in / out referendum the next time a British government signs up for fundamental change in the relationship between the UK and the EU.").
The Deputy PM went further by stating the coalition's EU referendum lock, which sees a public vote triggered whenever there is a transfer of powers to Brussels, meant that it was a question of "when, not if" a referendum would be held. It was the clearest signal Clegg has ever given that he believes a referendum is now inevitable at some point in the next three-four years.
In a notable attempt to narrow the distance between himself and Cameron, Clegg said that while the coalition's position on a referendum was clear, Labour had voted against the referendum lock. It's worth noting, however, that since then Miliband has explicitly stated that he would not repeal  the legislation. With the negotiations over the post-crisis shape of the EU likely to significantly change Britain's relationship a EU, a referendum looks increasingly inevitable whichever party wins in 2015.