The scare stories are not working. Millions of British people can already imagine a future outside the EU – and it is not one that terrifies them in the slightest.

To win the referendum, the In campaign needs big figures and big arguments. In Gordon Brown, it has both. The former prime minister will always have critics, particularly on the right, but today he made a direct appeal to Labour and non-Tory voters with a sweeping speech that shunned the politics of fear in favour of the passion of the positive.

Brown moved from the global and the historical to the local and modern. He took in Britain’s long and awkward relationship with the EU – from the time George Brown became “tired and emotional” on a trip to Vienna, to Margaret Thatcher’s tub-thumping in Bruges and her battles with tabloid nemisis Jacques Delors – and made the case for the bloc on the basis of its record in helping to deliver change, equality and economic and social justice.

And he refused to take part in Project Fear, the Government’s frenetic attempt to alarm people into sticking with the status quo, which saw its latest iteration today when George Osborne warned a vote for Brexit would send house prices tumbling by 18 per cent.

Instead, Brown sold us the value of the present and the opportunity of the future. The EU is already vital now, he reminded us, its members dominating the list of nations to which Britain exports, and leading co-ordinated action to tackle climate change.

And the EU will be just as vital in the future, he told us. The bloc will help Britain tackle a host of market problems: “zero hours contracts, the casualisation of Labour and exploitative employers”. He reeled off the list in the fast and familiar Brown fashion.

As is so often the case, Brown spoke without notes and for around 45 minutes. How does he do it, we wondered.

He strode the stage of the Fabians summer conference, hands a typical whirlwind of movement, reciting the successes of the EU, such as its work in trying to “stop the good employer being undercut by the bad, and the bad by the worst, in a dog-eat-dog race to the bottom”.

There were a few nice jokes, not all of them new, but a good one with which to bait Donald Trump. When asked to name his three greatest Americans, the presumptive Republican presidential candidate answered by saying “the other two are George Washington and Abraham Lincoln.” It worked all the better for the fact it came from Brown, a man known for his humility and taste for modest living.

Of course, Brown concluded on a heavyweight tone. Much of the left has been gripped by the revelations of tax avoidance of the last few months and Brown urged Britons to stay in the EU because it would be the only way to ensure governments combine on a clampdown.

“If you want to deal with tax havens then there is no way to deal with it other than the EU. There should be no treasure islands for the richest people in this country. There should be no safe havens for tax avoiders.”

For Brown, the political is always wrapped up in the moral. So he finished be evoking the battlefields of Europe in which British soliders had fallen over the last two centuries: Arnhem, Ypres, the Somme and Crimea.

Today, by contrast, Europe is at peace – and that is no accident.

“By the force of argument and not the force of armaments… we have exchanged swords for ploughshares in a way that we may never have to pick up swords again,” he said.

We deliver more when we work together, he reminded us, as he quoted Labour’s Clause IV. “By the strength of our common endeavour we achieve more than we achieve alone.”

It was the best case yet for the left to vote to stay In.