Fittingly perhaps, the PM gave his long-awaited Europe speech in a bunker, deep underground in the City of London, at Bloomberg's chrome and glass European HQ.
Hair swept neatly back, the shiny-faced premier bounced on to the podium, safe in the knowledge that most of his audience, the journalists at least, had been up since 4.30am and were only half-awake.
The backdrop behind Mr Cameron gave the game away. It read "Britain and Europe" rather than Britain in Europe.
It was what Mr Cameron did not say that was interesting.
He was asked if he would lead the campaign to get the UK out if these nice Europeans refused to give the Brits a renegotiated settlement.
He didn't answer but insisted he never entered any negotiations expecting to fail.
Four hours later, the calm of the City was replaced by the raucous cauldron that is the Commons. As soon as Mr C appeared, there was a loud cheer from the ranks of the Tory Eurosceptics, then an ironic one when Ed Miliband turned up.
Amid the hullabaloo, the Labour leader calmly picked up on the PM's non-answer in the City and not one but four times asked him if he would campaign to stay in the EU.
When the Tory chief declared he wanted a strong Britain in a reformed Europe, Labour MPs broke out into exaggerated laughter but Mr C tried to turn the tables and asked if his opposite number had a clue what he would do. Tory MPs shouted: "Answer!"
Mr M insisted that four hours after his big speech the PM could still not answer the question, which got Tory backbenchers pointing accusingly at the Labour leader for his cheek.
All the time, Nick Clegg, slunk in his seat, appeared to be biting his lip and squinting with pain; Coalition is not easy.
The SNP's Mike Weir then asked why the PM thought Scotland's two-year referendum process was too long but his five-year euro marathon was fine.
The PM replied: "The Scottish Nationalists, in my view misguidedly, want to leave the United Kingdom as it is. I will be arguing... Scotland should stay in the United Kingdom. What I want is to see in Europe is a changed Europe and then we ask the people."
Another non-answer and this time it was the SNP MPs' turn to fall about with laughter. It's going to be a bumpy ride to 2017.