Lithuanian President Dalia Grybauskaite, British Prime Minister Theresa May and Belgian Prime Minister Charles Michel | Emmanuel Dunand/AFP via Getty Images brexit files insight May’s rights offer falls flat on its face The main source of the EU’s displeasure was the nature of the offer.

Well, that didn’t quite go to plan.

It was supposed to be a "big and generous" offer that would start the negotiations off on the right foot. Theresa May would even personally brief EU leaders on her plan for how to safeguard the rights of 3.2 million EU citizens residing in the U.K. ahead of its official publication to reassure them.

Good idea? No. At least not the way she went about it. The U.K. prime minister leaves Brussels today with the EU27 more annoyed than they were before she arrived.

Partly this is about style. May is not the world’s best communicator. Telling EU leaders over dinner not to worry and that no families will be split up because of Brexit only riled the other leaders sat around the table — and EU citizens in the U.K. who are still worried about their future status. Their private reaction, briefed out by aides later, was: Why are we even talking about families splitting up? Is this how far we've fallen?

Much of the problem was choreography. Announcing the broad outline of the proposal without the details only served to expose the uncertainty which surrounds this issue. "Wait until Monday to find out the nitty-gritty," is not a great answer.

However, the main source of the EU’s displeasure — and that of the U.K.-based groups representing the 3 million EU citizens in Britain — was the nature of the offer itself.

Much of that can be easily overcome. Despite the initial reaction in Brussels, there is willingness on the U.K. side and that will go a long way. The U.K. government was expecting kickback but believes, when the dust settles and the full details are published on Monday, there will be wide acceptance that both sides are moving closer to a deal.

But first, on the substance: The EU is unhappy with the proposed five-year residency requirement before EU citizens can acquire their full rights. What happens if you had moved to the U.K. in good faith in May 2016, one month before the referendum? When the U.K. leaves the EU in March 2019 you won’t meet the requirement to have your rights fully protected.

There is also concern about the lack of a cutoff date for new arrivals.

However, campaigners in the U.K. say it is on these types of issues that consensus can be built in a negotiation. They are not deal-breaking problems.

It is the second issue which remains far more problematic. Put simply, the EU thinks the U.K. does not treat immigrants very well. The Home Office’s 80-odd page checklist is now infamous in Brussels.

In the U.K., Brussels is a byword for out-of-touch, bureaucratic government. It is an irony of the Brexit negotiations that that is now Brussels’ view of the U.K. In effect, the EU does not want its citizens left in the U.K. at the mercy of the Home Office. It argues that they need to be protected by impartial judicial oversight. And since these are EU rights, that should come from the European Court of Justice in Luxembourg.

For London, being under the control of a foreign court is an unacceptable infringement of sovereignty — and besides, its judicial system is respected around the world.

Everything else can be negotiated. But unless there is movement on this question — from both sides — Brexit is going to fall at the first hurdle.

This insight is from POLITICO's Brexit Files newsletter, a daily afternoon digest of the best coverage and analysis of Britain’s decision to leave the EU. Read today’s edition or subscribe here.