Brexit Minister David Davis has refused to provide a methodology for how Britain's financial obligations to the EU should be calculated | Emmanuel Dunand/AFP via Getty Images UK Brexit charm offensive falls flat EU diplomats briefed by a senior UK official said promise of more clarity on Brexit bill wasn’t kept by London.

It was meant to be a charm offensive directed at national capitals across Europe to help smooth the Brexit negotiations — but the British government's decision to hold confidential briefing sessions for EU ambassadors in London appears to have fallen flat.

In the last two weeks, the U.K. held two such events in a bid to explain London’s negotiating positions on key issues ahead of the latest round of Brexit talks, which are now underway in Brussels. If the effort was intended to win a sympathetic ear, it flopped.

The meetings have not been officially announced, but according to six senior diplomats POLITICO spoke to who were either present at the meetings or briefed on them, the representatives of the EU27 were not impressed by what they say was a lack of detail from the U.K. And they were dismayed that a promise to provide a detailed position paper on how to calculate the U.K.'s financial obligations to the bloc once it leaves was subsequently withdrawn.

The hour-long briefings — which took place on August 17 and 24 at the U.K. Foreign Office in Whitehall — were given by Alex Ellis, director general of the Brexit department and a senior member of David Davis' negotiating team. On the invite list for the first meeting were representatives from all EU27 countries. At the second, the invite list was extended to include Iceland and Norway.

"Ellis basically told us that the purpose of the papers was to show to Brussels that London had done its homework this time" — A senior official

The first briefing covered the U.K.'s papers on customs and Northern Ireland. The second session was on five papers that laid out the U.K. position on topics including data protection and European Court of Justice jurisdiction. Ellis also promised more position papers from the government in the coming weeks.

"He told us that we had to treat the papers as simple 'policy proposals aimed at starting a dialogue' in response to EU papers and that their main purpose was to 'to share ideas,'" a senior official who attended both briefings said. "Ellis basically told us that the purpose of the papers was to show to Brussels that London had done its homework this time."

The Brits were stung by what they saw as unfair criticism that they were unprepared, after the second round of talks in July.

But according to two officials in the room, when two ambassadors and a deputy ambassador pressed Ellis to provide more information on how Britain's customs plans could be implemented, he was unable or unwilling to provide detailed answers. A second diplomat said the whole presentation came across as "very vague and ambiguous."

As adversaries in the Brexit negotiations, EU diplomats could have an incentive to present the U.K.'s position in a less than favorable light. But apart from their reaction to what Ellis had to say about the U.K.'s first two papers, another cause of consternation was his alleged promise at the first of the two briefings in London of more clarity on the Brexit bill.

"Ellis had announced at the end of the first meeting [that the UK would provide a position paper] on Britain's financial obligations," said a diplomat who attended both meetings. "[At the second meeting] Ellis said that such a paper was actually not going to be published and that with respect to the divorce bill the U.K. had gone as far as it had to by acknowledging in the second round of talks that it owed money to Brussels."

The prospect of a detailed position paper laying out Britain's thinking on how to calculate the Brexit bill is significant because the U.K.'s stance on the issue has become a key sticking point in the talks. While Davis has acknowledged that his country has financial obligations to the bloc, he has refused to provide a methodology for how Britain believes they should be calculated — preferring instead to critique proposals on the bill from the other side of the table.

The approach has infuriated Brussels, with EU chief negotiator Michel Barnier imploring Davis at the start of the latest round of talks on Monday: "We must start negotiating seriously."

That the U.K. allegedly dangled the prospect of serious engagement on the Brexit bill as recently as mid-August will raise eyebrows in Brussels and suggests either a diplomatic mistake or a last-minute change of negotiating tactics.

A spokesman for the U.K.'s Department for Exiting the European Union (DExEU) confirmed that the London meetings happened, but said: "We don't recognize this account."

"There is still a huge split between the technical side and what can actually be said politically" — An EU diplomat

"There have been a series of briefings for EU embassies in London on the contents of the papers we have published in recent weeks, at which officials from across government have responded exhaustively to a wide range of questions on the content of the papers, on customs, Northern Ireland and many other issues," he said, adding, "We will continue to provide detailed information for our EU partners on our policy thinking."

After publication of this story, DExEU offered POLITICO a further statement: "It is completely false to suggest we promised a paper on the financial settlement — in fact, officials downplayed any expectation that there would be one. We have already published 11 position and future partnership papers."

Outside observers say that too much clarity at this early stage in the negotiations may not serve the U.K.'s interests. "Why would you as the U.K. capitulate on everything the EU wants now before receiving any guarantees of your own?" said Pieter Cleppe, who heads the Brussels office of Open Europe, a right-leaning think tank based in London. "It would be political suicide."

Some EU diplomats say they believe the British ambiguity stems from the disconnect between ministers and technical experts in the civil service on key aspects of the U.K.'s negotiating stance. "There is still a huge split between the technical side and what can actually be said politically," an EU diplomat briefed on the London meetings said. "Technical officials in Britain know these issues well, but what they can say about them is so constrained by what is happening politically in the country. It's very difficult for them."

The London briefings are part of a wider engagement effort by the Brexit department and the Foreign Office, first revealed by POLITICO earlier this month, to better communicate the British government's position without going through the European Commission negotiating team.

This article was amended on 30 August 2017 to include a further statement provided by the U.K. Department for Exiting the European Union.