Brussels wants everyone to know it is still in charge in the Brexit talks.

The European Commission last week warned member countries against allowing their officials to attend a series of bilateral seminars on Brexit put on by the U.K. government in London, according to EU officials and diplomats.

At a regular meeting of EU27 Brexit officials last Friday, held to debrief diplomats on the latest round of talks with the U.K., the Commission said it has been made aware of the London events put on for EU27 diplomats and billed by the British government as "technical seminars."

“[The Commission] urged member states not to engage in bilateral talks,” said one of the diplomats, who added that several countries confirmed they have been approached by the U.K.

The U.K.'s approaches to member countries come at a crucial time in the talks, with less than seven weeks until the supposed deadline for an agreement. So far, the EU's negotiating strategy has held firm against attempts by London to drive a wedge between national capitals in order, potentially, to gain an advantage in the talks.

While individual countries have welcomed British ministers to national capitals to discuss Brexit — notably during a summer blitz of U.K. diplomatic activity to sell Theresa May's Brexit white paper — they have stuck firm to the line that negotiations can only happen through Michel Barnier's Article 50 task force in Brussels.

“No deal means no deal. No deal does not mean that we will negotiate a series of mini deals" — Official

The Commission is concerned that any substantive bilateral talks would derail that EU negotiating strategy and allow British negotiators to gain an advantage through a divide-and-conquer approach. “It seems like a British attempt to sideline the Commission,” one EU27 diplomat said.

In a speech accompanying the release of a series of papers outlining preparations for a no-deal scenario last month, the U.K. Brexit Secretary Dominic Raab made clear that in the event of a breakdown of the talks with Barnier, he expects a series of mini deals would be necessary to mitigate the impact on both sides of the Channel.

Some of these mini deals with the Commission may “not necessarily be legal arrangements,” said Raab, adding that they could also be made with individual countries or regions, or national institutions directly.

One idea in Brussels is that some of the London seminars might be aimed at scoping out such bilateral mini deals if the main Brexit talks break down irrevocably. But one EU official said the EU27 should reject that approach. “No deal means no deal. No deal does not mean that we will negotiate a series of mini deals,” the official said.

One of the diplomats said the message from the Commission at Friday's Working Party Article 50 meeting was: "We’ve explained everything that you should know, if you have more questions we’re always ready to provide answers. There’re absolutely no need to go to these seminars."

The Commission itself “will not take part in these seminars,” said a second EU27 diplomat, who also confirmed that member countries have been urged by Commission officials not to attend.

A third diplomat who was at the meeting said the message to member countries was to urge "caution" and “to stick to the common line if approached [by London].”

In response to the seminars, the Commission is preparing a document detailing a common approach for member countries to follow that will likely be distributed via the European Council next week, according to one of the diplomats. But some officials said they feel the move is unnecessary because the EU27's common line is already spelled out in the Council's guidelines — Barnier's mandate for the negotiations issued by the 27 member countries. The Commission's intervention “caused a bit of agitation,” said the second EU27 diplomat.

The third diplomat said there was no heated debate during the meeting, though, and that many diplomats there pledged their "support to Barnier and unity of the EU.”

A fourth diplomat said there is no chance of member countries abandoning the Commission-as-negotiator approach at this stage of the talks. Only "at the very last second" might that change, the official said, if the talks are breaking down but leaders see a way to rescue them.

Asked about the nature of the London seminars, a spokesperson for the U.K.'s Department for Exiting the EU said: "As you would expect, following the publication of the white paper, DExEU has been engaging with a wide range of people, businesses and organizations to explain our proposals for an ambitious future partnership with the EU. This includes engagement with London-based representatives of EU member states."

"We will continue these conversations throughout the Brexit process, as we deliver a deal that works for the U.K. and the EU," the spokesperson added.