That was a turning point in our history. It marked the start of our rejection of the concept of a federal United States of Europe and of the suppression of nationhood.
Mrs Thatcher wryly acknowledged that her presence at the College of Europe might seem to some like inviting Genghis Khan to speak on the virtues of peaceful co-existence.
Yet it was far from being an anti-European speech. Indeed, after emphasising our European ancestry, culture and contributions to its liberty – 120,000 British soldiers lying buried only a few miles away – she said our destiny was in Europe as part of the EC. The unspoken question was what kind of EC.
It is the failure of Europe to provide a satisfactory answer that led to us voting to leave the European Union next March.
Brussels cannot argue that Mrs Thatcher failed to give due warning or to offer a blueprint for the future.
She told them: “We have not successfully rolled back the frontiers of the state in Britain only to see them re-imposed at a European level with a European super-state exercising a new dominance from Brussels.”
Her blueprint was willing co-operation between sovereign states. encouraging change, facilitating enterprise, free markets instead of ever more detailed regulation from the centre, while being open to the world and strong in defence through Nato.
I am as certain as anyone can be that we would never have heard of Brexit if Europe had taken heed.
Instead they ignored her, steadily building a federal Europe regardless of the people’s wishes.
If voters rejected ideas for further integration, these were either “re-packeged” or the dissidents were coerced into voting again – as the Irish, Danes, Greeks, French and Dutch demonstrate.
What made me vote wholeheartedly for Brexit was my experience of the EC, attending 31 consecutive European summits with Mrs Thatcher and a number of EC Energy Councils with Tony Benn before that.
I grew progressively fed up with its undemocratic nature, its insensitivity to, and even contempt, for public opinion, its centralisation of power, its pretensions and the inequality of membership with smaller states begging like dogs for morsels to fall off the Franco-German table.
The single currency, and its devastation of southern Europe with unemployment, have added to my disaffection. And all the while our and Europe’s Establishment “elites” ignored the damage to our democracy. Why bother electing governments that are not in control of national affairs?
It should surprise no one that we are now coming to the crunch. In facing it, the Labour Party is tragically irrelevant except as a wrecker.
Its leader, Jeremy Corbyn, is owt for tuppence if it will defeat the Tories after life-long opposition to Europe as a capitalist ramp.
I suspect no one, least of all, Theresa May, thought that departure would be easy. Yet Emannuel Macron, the French president, calls me and 17.5m other Britons “liars” for claiming it would be. He speaks volumes for the European elite’s nasty vindictiveness.
They are there to make life so awkward for us that, to utterly misread the British character, we will think twice about it.
As the Tory conference looms we need to recognise that, notwithstanding her current refusal to chuck the Chequers plan already rejected by the EU, Mrs May is in a strong position.
She has bent over backwards – too far for her own and our good at times – to try to secure an acceptable agreement. And all the European Union’s negotiators say is “Non” and then try to humiliate her.
In Salzburg she told the EU to come up with Brexit terms her party can accept or we leave with no deal.
All she needs now is manifestly to secure our independence and control over our borders, trade and laws and she is a heroine.
If there is no deal, temporary disruption may well follow but other European states will suffer, too. We shall, however, have recovered our sovereignty. What a prize!
In conference next week every sane Tory, especially when faced with the Corbyn alternative, should give Mrs May the chance to secure acceptable terms and then come together to build a new Britain just as Margaret Thatcher did.
It should be obvious to them that many aspects of British life need urgent remedial action.
And only – repeat only – the Tories these days can deliver it. They must show maturity and responsibility. Come on, grow up.