Speeches were held by leading politicians including Prime Minister David Cameron at the British Museum in central London about the looming EU referendum.
Here are five things we have learned about the EU referendum today:
1. The music choices were interesting
Someone in the Leave campaign was certainly having fun with the warm-up music to Boris Johnson's big speech as "The Final Countdown" by Europe was followed by Fleetwood Mac's "Go Your Own Way".
But, perhaps the most fitting track of all was "Love Will Tear Us Apart" - but was that a reference to the future of the EU, or the Conservative Party itself?
Not to be outdone by the DJ, the former London mayor at one point broke into song himself as he celebrated Europe Day by singing a few words of the EU's anthem, "Ode To Joy", in German to prove he was "not a Little Englander".
After announcing that he was a "humble ex-municipal toenail", Johnson then cited one of the reasons we should quit the EU was because there is no "common sense of humour".
But his performance could well have united the nations of Europe in laughter - at him, not with him.
2. Boris Johnson delivered a spectacular put-down
Boris did deliver one stinging put-down when he was asked about Chancellor - and Conservative leadership rival - George Osborne's spiky comments that the next top dog of the Tory party needed to be "sensible, sober, and credible".
Johnson replied: "I'm delighted to discover that the Chancellor is principled, it is important - and sober - and everything else. A very important development."
3. There was a lot of symbolism
So much symbolism in the choice of the British Museum for Prime Minister David Cameron's "patriotic push" speech for the Remain side as the grand building exemplifies a country proud of its past, yet the setting in the magnificent Sir Norman Foster-designed Great Court - with its glass ceiling that left the Prime Minister dappled in bright morning sunshine - also signified a modernist nation looking forward to the future.
And the exhibitions advertised on the walls close to the PM's podium also offered something for everyone as the one cited "Sicily: Culture and Conquest" could surely exemplify the Leave camp's fears that Brussels is set to reduce this once great island fortress to colonial status with its culture and identify plundered, while the "Sunken Cities" exploration could be a prophetic warning of the post-Brexit fate of the City of London's financial services.
4. Cameron warned about losing Scotland
As if the looming possibility of a housing crash, deep recession and the Third World War were not enough to scare everyone into the Remain camp, David Cameron also warned that Brexit could smash up Great Britain as Scotland may take it as a cue to finally say goodbye.
So what kind of reckless political gambler would risk all this disaster by holding a referendum in the first place? Oh, that's right - David Cameron.
However, the Prime Minister dodged the question when asked why he had thrown the future of the nation - and apparently the peace of Europe - into such uncertainty.
5. David Miliband had a few words to say
As Ukip rejoiced at a poll showing publicans in favour of a pull-out, the hangover from Labour's last-but-one leadership battle may well have been weighing on the mind of former foreign secretary David Miliband as he introduced Prime Minister David Cameron for his set piece speech.
It must have been a bittersweet moment for Miliband. Well, he is still probably a touch bitter at brother Ed's sweet cheek at stealing his crown in 2010, and, just maybe, if that had not happened, then the David in Downing St today could well be the Labour one, and not his Tory namesake - meaning we would likely not be having this referendum at all.
With Sadiq Khan firmly installed in London's City Hall, bookies are offering odds of 8/1 on Miliband taking the Mayor's Tooting seat at Westminster in the looming by-election.
Such a (very unlikely) move could well herald a Jexit crisis for Jeremy Corbyn not long after the Brexit battle is decided.