One contribution from the floor gave me a clear sign of the mountain that those of us in the pro-European camp have to climb. A speaker rose and proclaimed that he had been born in Swansea in October 1939, and was there when German bombers tried to obliterate the city. He went on to say that we had won the war, and secured our freedoms, and that we had no right to deny historic British liberties to future generations by joining the euro. I was more struck by how far this perspective summed up much of the anti-European case. That case is not at all sophisticated. The sceptics try to say that it is, by suggesting that they are not anti-European, but anti-euro.
In fact, the two amount to much the same thing, because by and large the anti-euro case is imbued with near-paranoid fears over domination from the Continent, and a belief that by joining the euro we would be ending hundreds of years of proud independence. Heard it all before? I remember much the same being said by the doom-and-gloom merchants when our currency went decimal; they trotted out the same argument against the Channel Tunnel.
At the heart of their case is a profound sense of fear - and this is where pro-Europeans can take heart. The antis will exploit fear as much as they can when we eventually have a referendum on joining the euro. And the people doing so will indeed be a fearsome bunch.
Picture it: Margaret Thatcher, Tony Benn, Norman Tebbit and William Hague, perhaps even Ian Paisley, together at a press launch, ranting about the dangers of the euro. Ranged against them will be an altogether different group of people: Tony Blair, Ken Clarke, Gordon Brown, Michael Heseltine, and the next leader of the Liberal Democrats.
Whom will the British people believe? The old guard of discredited, backward- looking politicians? Or will they support the most popular Prime Minister this century and his Chancellor, working constructively with mainstream and respected figures from two other parties? I believe that the answer is clear. But we need to start working now, and we need to settle on some clear messages.
First, we must persuade people that it is patriotic to be pro-euro, because it will be good for Britain. I am not in politics to damage British interests. Far from it. One of the pro-devolution arguments that I always found most persuasive was that devolution would help save the Union, and I firmly believe that it will. I equally believe that joining the euro will help Britain, because in purely selfish terms it will enable our businesses to access the EU single market of more than 370 million people on entirely level terms with Continental businesses.
And as the euro will be a major player in the global financial markets, it will be invaluable in securing the economic stability that British business must have.
A second, and related point, is that only by being constructively engaged in Europe can Britain actually have a real influence on the shape of the EU. No serious politician advocates withdrawal from Europe, yet unless we are willing members, we will end up dealing with the consequences of decisions that affect us, but on which we have had no influence. There were real opportunities for Britain to take a lead in Europe in the late 1940s and 1950s. But Britain instead preferred to cling to the imperial idea, and the falsehood that full involvement in Europe would damage Anglo- American relations. On this case, I am always struck by the comment made by the former US Ambassador to Britain, Raymond Seitz: "If Britain's voice is less influential in Paris or Bonn, it is likely to be less influential in Washington."
Yet Britain missed the boat when the Treaty of Rome was signed; it had no influence, and the consequences were reaped when finally it did decide to join, was rejected twice, and eventually entered on unfavourable terms.
Mr Blair and Mr Brown must also recognise that Britain will not be manoeuvred into the euro by stealth. There are serious arguments to be had. We particularly need to hit back at the anti arguments with a vigour that we have not seen in the past. We are told, for example, that our economy is more world-oriented than the rest of Europe. Not so: four of the existing 11 members of the euro-zone export more of their GDP outside the euro-zone than we do.
They say that Europe is mired in recessions, and we should steer clear of this bunch of losers. Rubbish: Europe is growing faster than Britain is. And we are told that the euro has fallen dramatically against the dollar. True: but if currency strength or weakness against other currencies were the test of a currency, we should have ditched the pound years ago. In 1966 a pound bought 11 German marks. Last week it bought just three.
While we hit back at arguments against the euro, we also need to highlight the deficiencies in the Hague vision. What does he actually want? He seems to want a free trade area with no strings attached.
But Efta failed, and broke up. Or perhaps he wants to get out of Europe, as splitting with the European People's Party would signify. His vision is far from clear, and there is a great danger that Hague would only lead the UK up a blind alley.
At the heart of our campaign, then, should be the idea that joining the euro would be a patriotic move for Britain, as it would be good for our interests, and allow us to exert a real influence in Europe. And we should hit back hard at the arguments pushed by Hague and others, while highlighting the paucity of their own alternative.
But before all this, there is one strategy issue that we must get right. Earlier I put forward a vision of a pro-euro campaign led by the mainstream figures of British politics. For that to work, the pro-euro Conservatives must be brought on board - and soon. That means the people who stood under the pro-euro banner, but it also means people such as Clarke and Heseltine who are still, somehow, in the Hague Conservative Party. Without their support we will struggle to get the message across. There is much work to be done over the months and years to come, in making it easy for them to join with like-minded people in other parties. The prize is great. It is a challenge I relish.