Sitting at her desk, Theresa May is drafting her Florence speech for Friday. The time has come, she finally decides, to put country before party; to abandon the vain attempt to bind together her party’s utterly incompatible factions. What’s the point? There’s no possible EU deal that would induce John Redwood and Liam Fox to agree with Anna Soubry and Ken Clarke, no fence left to sit on. She must become the prime minister no one thinks she is.

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“The time has come,” she writes, “to face the truth about Brexit. Our people have voted to leave, and so we shall. But no one asked how, on what terms or at what national or personal sacrifice. Nothing on that small ballot paper gave me any clue as to what each of 17,410,742 voters had in mind. So it falls to me to interpret the people’s will. And, as my chancellor says, no one voted to become poorer.

“In the 15 months since that vote, I have studied every option. I have listened to experts – yes, I believe in expertise. Businesses small and large almost with one voice warn that leaving the single market and the customs union risks devastating manufacturing, finance and services. Already we see banks and companies setting up new headquarters across the Channel. I see talented Europeans ready to depart, not least from the NHS: they need reassurance now.” The words begin to flow.

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“To stay within the single market and the customs union, we must pay our dues: we will strike a fair price, fair for the gain that buys our economy. We will leave the EU’s councils and its parliament, as the vote requires. But we are not leaving our closest neighbours and old allies. Instead we shall seek to stay in the EEA, alongside a country like Norway, which is thriving. And so shall we. There is no other solution to the problem of the Northern Irish border: the EU cannot leave open a back door; and it is my duty not to jeopardise the hard-won peace agreement. Nor will we put at risk the great good brought by all our fellow European citizens who have chosen to live with us, interwoven in the rich fabric of our cultural life.

“The time has come to refute the delirious fantasies of those who have led us out of the EU. My colleague Boris has just given another firework display of his own imagined glorious future. Words are his milieu, but mine is the real world in which ordinary people earn their living and hope to flourish. I have yet to see from him, or any of those who would plunge us over the cliff edge, any details as to how cutting off half our trade will do us anything but harm. I am shocked any minister of mine would wilfully ignore the chair of the UK Statistics Authority on a matter of fact.

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“Some will still follow these pied pipers spinning airy dreams. No doubt some will challenge me. But I will stand and fight for the interests of my country against the whims of elements in my own party. I am prime minister of the country first, leader of my party second. Protecting the people is my prime duty, and I will condone no damage to all who have already suffered a hard decade since the start of this global recession.

“Judge me not as a party politician, but as a prime minister delivering my people’s wish to take Britain out of the European Union while seeing our country thrive and prosper. Out of the EU, yes, but we will stay close to our good neighbours after 70 years of mutual prosperity and peace. Here in Italy, as in France, Germany and all the EU nations, we rely on one another’s strengths and our common civilisation in a dangerous world. In Brexit, Britain will neither harm itself nor its good friends.”

Her peroration complete, she sits back to consider the words she has written, sighs, crumples the paper and throws it into the bin. She dare not, after all.

• Polly Toynbee is a Guardian columnist

• This article was amended on 27 September 2017. An earlier version said Switzerland was in the EEA, it is not.

