We are approaching what Alex Ferguson used to refer to as “squeaky bum time”: the summit at which EU leaders will decide whether “sufficient progress” has been made on article 50 negotiations to allow trade talks to start kicks off on 19 October. Michel Barnier, the EU’s chief negotiator, has set October 2018 as the tentative date for the end of the negotiations as a whole. Moreover, the longer the talks continue without visible progress, the more businesses will start planning and preparing for the worst, “no deal” scenario – which will not be good news for the UK. So there is much to be done. And not much time to do it. Consequently, Theresa May’s speech in Florence on Friday is of crucial importance.

So what should she say? The priority, given the timetable, is to unlock the article 50 talks. This, first and foremost, means some movement on money. Of course the government would prefer to use money as a negotiating chip when it comes to the trade talks. And of course discussing how much we will pay the EU is politically tricky, to say the least. But it is time to be honest and admit that the government has lost the former battle and has to fight the latter one. Without movement on this issue, there will be no movement at all.

And while the misnamed “Brexit bill” is the most pressing issue, Theresa May would be well advised to acknowledge the central importance of the two other key article 50 subjects. Any deal that does not satisfy the EU when it comes to its citizens could conceivably squeak through by majority vote in the European council, but it is hard to see the European parliament, which wields a veto, acquiescing.

The mood music of “deportation letters” ordered by an overstretched and increasingly incompetent Home Office has hardly helped. Moreover, there are real issues to be addressed concerning the long-term protection of the rights of EU citizens. Anyone watching our parliament at the moment will understand why Brussels is not anxious to place its faith in that institution.

Moving beyond the divorce, the other pressing issue May must deal with is what could be termed the “period of uncomfortable cohabitation before one partner secures a new place to live”. From open warfare in the cabinet to apparent consensus in the cabinet and back again with Boris Johnson’s latest intervention, transition has been the summer pantomime. But now it seems the government views it as key to sorting out the “Brexit bill”.

Be this as it may, there are several things the prime minister could usefully clear up. First, she could ditch the notion of an “implementation phase”. It is well past time to put to bed the idea that we will have sorted out a complete trade deal by October next year. So we need time both to negotiate and to implement.

Second, transition must resemble either the status quo or the final deal. There is no way the other member states will want to make two sets of adjustments to their trading arrangements simply to accommodate us. Because we won’t know the shape of the final deal we are talking status quo. British businesses and the Treasury have long been arguing for this, and they are now joined by the Labour party, so it’s the closest thing to a consensus in UK politics. The prime minister should say this loud and clear.

And when it comes to the final deal itself, while it is clearly too early for fine details, some broad-brush ideas would be helpful. Simply reaffirming, again, that we want to cooperate and have done so effectively for years will not cut the mustard. A Boris Johnson-style disquisition on the Renaissance and Winston Churchill is neither what our partners want nor what we need.

The key point here is that choices too long delayed now need to be made. We have, of course, been here before. The two of us, prior to the Lancaster House speech, advised the prime minister to address what we called the “cake issue”. But we understand she may be too busy to read all our work, and we are nothing if not persistent.

Brexit involves trade-offs. Having and eating cake is not an option.

So, to recap. If we want to be in the single market we will need to obey the rules. If we want the customs union, likewise. We can’t avoid a border in Ireland just because we’d like to. The European Union won’t buy the touching faith in unspecified technologies the government seemed to rely on in its paper on future customs arrangements.

Any attempt by the prime minister to address these choices would underline that she is serious about the negotiations. It is decision time, and the prime minister will need to make decisions, however hard it might be to bring her cabinet with her. Does she want a Nigel Farage Brexit – a Britain where train passengers all speak English and drink warm beer, and our key international relationship is the “special” one with Donald Trump? Or a Liam Fox and Boris Johnson Brexit, a “global Britain”, leaving the insular and protectionist continentals behind? Or a Philip Hammond (and Keir Starmer) one, where we are outside the political structures of the EU, but the rest of Europe remains by far our most important economic and trading relationship?

And finally, in the unlikely event that the prime minister heeds our plea for clarity, it will all be for nothing if an away win in Florence is followed by defeat at home in Manchester. Detailing what we want to our partners while decrying them and their demands at the Conservative party conference is not clever tactics, but self-defeating hubris. It is time our leaders realised that our partners listen to what we say at home as well. While Sir Alex instilled a “no one likes us” siege mentality, it is not a sensible way to deal with Brexit.