Michel Barnier, the EU’s lead Brexit negotiator, finally took the stage on Tuesday after three months of backroom preparations, 18 trips to member states and one meeting with a British minister.

“All of you will understand it is too soon to talk today about the details of Brexit,” he said to the packed hall of journalists, before duly laying down some cold truths for London on the limitations of its exit negotiation.

At times using measured English, the former French minister had three main messages: that Brexit talks would be a short negotiation lasting less than 18 months; that maintaining unity among the remaining 27 EU countries was his overriding priority; and that the final deal would have to be worse than EU membership.

The response to Mr Barnier’s remarks reflected the growing gulf in expectations between Britain and the EU. To diplomats in Brussels, he expressed in relatively neutral tones some core principles that were agreed behind the scenes with little controversy.

Yet to British MPs, it was “grandstanding to Brussels” that was jeopardising talks. “Mr Barnier’s latest contribution is of just the type calculated to raise the political temperature at a time when he should be lowering it,” said Andrew Tyrie, who chairs the Treasury select committee.

Here is the FT’s guide to what Mr Barnier said, and what he meant:

“Time will be short . . .”

It may be the most complex negotiation in the world, but Mr Barnier reckons the EU has as little as 15-18 months to complete it.

Once the Article 50 withdrawal request is lodged, the formal EU separation process sets a two-year renewable deadline. But within that the EU must first agree its negotiating mandate, and make time to ratify any draft exit agreement in the European Parliament, between member states, and in Britain. Mr Barnier reckons the ratification process will take four or five months at least, making his target date for a deal October 2018.

“You cannot do everything in 15-18 months . . .”

The short timetable puts limits on what can be agreed. British ministers ideally want to agree a full EU-UK trade deal before departing the EU, and if that is not possible some kind of orderly, smooth transition to a future trade deal.

Mr Barnier’s message was that a “new partnership” would be discussed in broad terms, to give a sense of what the future relationship “may” look like. This would guide any transition terms agreed.

But his strong hint was that no complete trade deal would be possible within two years, and any transition would be “short”, negotiated quite late in the process and “difficult” to agree. For Britain the sequence matters. If transition terms are left to late 2018 then the arrangements are less valuable; business decisions would have already been taken.

“Cherry picking is not an option . . .”

This is a favourite cliché in Brussels when talking about any British demand for exceptionalism. It belies a strong consensus within the EU-27 over what is possible in any Brexit deal. Mr Barnier’s said the four freedoms of the internal market were indivisible — meaning the free movement of capital, labour, goods and services. The negotiating message there is particularly relevant to any transition: Mr Barnier was hinting that a bespoke deal, heavily tailored to UK political needs, was out of the question.

That would mean the UK would likely have to swallow things like contributing to the EU budget, only limited restrictions on EU migration, curbs on what laws can be changed, and the oversight of the European Court of Justice. That potentially sits uneasily with Theresa May’s description of the referendum result: “They voted for us to take control of our borders, they voted for us take control of our laws, and take control of our money, and how we spend our money.”

“Brexit is clear, ordered . . .”

These are important not only in preserving the integrity of the EU single market — and all the political compromises on which it is built — but also in settling outstanding budget bills from the EU budget, which the commission oversees. Mr Barnier did not mention UK liabilities, but has told colleagues he estimates the British exit bill to be as much as ‎€60bn. A clear settlement of these outstanding matters is, for Mr Barnier, the first step to building a new partnership.

“Keep calm and negotiate . . .”

Mr Barnier’s bon mot was a play on Britain’s wartime mantra to “keep calm and carry on”. This was an overture of sorts, reinforced by him delivering his opening remarks in fluent English (his command of which has improved significantly with lessons since 2009).

Mr Barnier does not want to be seen as anti-British, or to be blamed for bias if the talks go badly: he recalled that his first vote in France was in a referendum on the UK’s membership of the European Community — a decision he did not regret.

Some EU officials also wonder whether it is part of Mr Barnier’s own post-Brexit strategy; he has long coveted the job of Commission president, and command of English is still seen as almost essential.