Both sides need to chill. That’s basically the message (I’m paraphrasing slightly) from Donald Tusk, President of the European Council.

Tusk has called for ‘discretion’ (probably aimed at Jean-Claude Juncker and his leaky staff) and ‘moderation’ (probably a broadside at the Prime Minister and her ‘astonishing attack’ on the EU).

The Prime Minister wants to win an election. Fair enough. Tough rhetoric plays well with the electorate. The EU negotiators understand this.

However, this risks getting out of hand. Public expectation needs to be carefully managed otherwise the government will box itself into a corner.

People are being led to believe (possibly by a prime minister who believes it herself) that Britain shouldn’t have to pay a single penny as part of the so-called ‘divorce bill’. Politically, however, that would be impossible for EU leaders to sign up to.

The UK government has (before the referendum, and together with other European governments) made a series of financial commitments at the EU level. If the UK fails to honour those commitments then European leaders will have to go back to their own electorates and explain that they now need to stump up more cash to pay for things the Brits promised.

European leaders won’t accept the UK leaving without settling the bill because, ultimately, they are also politicians and they also need to think about winning votes. Even if they believed the UK was taking a reasonable position (and there is every indication that they don’t) their political room for manoeuvre is limited.

Not to mention that leaving EU governments in the lurch over Britain’s exit bill would almost certainly mean national parliaments getting a say over any final divorce deal, drastically increasing the chances of a messy break-up.

The UK won’t be expected to produce a novelty cheque to the tune of €100 billion. We don’t know what the final number will be, but it will almost certainly be less than the gross figures being bandied about by the Financial Times (£). For one thing, the total sum includes loans given to Ireland, Portugal, and other countries. When the loans are repaid, money would go back to the UK.

A sensible outcome would probably involve the UK agreeing to pay a (hopefully) reasonable sum in instalments until 2020 (and, in fact, probably 2025). The final figure is almost certainly up for negotiation. The principle of Britain paying some form of ‘Brexit bill’ is likely to be non-negotiable.

One final point about the tenor of the debate. There seems to be an assumption that the current bust-up is only temporary and things will go back to normal after negotiations have been concluded. Ruffled feathers will be smoothed down again and cordial relations will resume.

Notwithstanding the fact that EU-UK trade talks could stretch on for a decade, I fear that this view might be overly optimistic. Rather, it could be that we’re being treated to a sneak peek of Britain’s new relationship with Brussels.

On issue after issue – trade, security, foreign policy, climate change, etc. – European leaders will thrash out a coordinated response behind closed doors (doors that were previously open to us).

The 27 EU countries will constantly be ‘lining up against Britain’ on everything. If they’ve started doing it now, why should they stop after Brexit?