Take your marks. Ready. Set. Go.

Both the EU and the U.K. have published detailed negotiating positions and are now ready to fire the starting gun on the next phase of Brexit talks.

For both sides, these are unprecedented negotiations. Battle lines are drawn and slide wars are underway, and it's time to look each other in the eye and start talking to determine the future relationship between the EU and its former member country for decades to come.

POLITICO has you covered for everything you need to know about this next phase of negotiations.

The players

Michel Barnier: The European Commission chief Brexit negotiator has won plaudits from across the EU for his work on the first phase of the Brexit talks, especially for maintaining unity among the EU’s 27 countries. German Chancellor Angela Merkel went so far as hailing the Brexit deal as a “diplomatic masterpiece.” EU diplomats also praise the patient consultation and consensus building of the former French minister.

Clara Martínez Alberola: Michel Barnier’s deputy is new to the Brexit job, but Martínez Alberola knows the drill. As one of the first Spaniards to join the EU’s civil service after Madrid’s accession to the bloc, she has spent her entire career in EU institutions and is known for combining cross-sector knowledge and management skills with political smarts.

João Vale de Almeida, the new EU ambassador to the U.K., will be in the room for the high-level negotiations alongside Michel Barnier.

David McAllister: As chair of the European Parliament’s U.K. Coordination Group, the German MEP David McAllister is the new Guy Verhofstadt, leading the Parliament’s position on the future relations with the U.K. McAllister, a member of the European People’s Party, is also chair of the foreign affairs committee.

Didier Seeuws: As head of the Council’s Working Party on the U.K., Belgian Didier Seeuws is responsible for maintaining unity among the EU27. Shuttling between capitals in order to iron out differences will not be an easy job as each country has its own interests to think of and every one of the 27 gets a veto on the final deal. Given the tight timeframe of the talks, trade-offs might be necessary sooner rather than later.

João Vale de Almeida: The new EU ambassador to the U.K. will be in the room for the high-level negotiations alongside Michel Barnier. The Portuguese diplomat has served as the bloc’s ambassador to the U.N. and the U.S. He joined the European Commission in 1982 after working for a time as a journalist.

David Frost: A former adviser to Boris Johnson in the Foreign Office who was poached from his job as CEO of the London Chambers of Commerce to become chief EU negotiator when Johnson returned to government as prime minister. Frost was a behind-the-scenes operator during talks on the Withdrawal Agreement and won plaudits for renegotiating the Northern Irish backstop. He was kept on as lead negotiator for the trade talks and looks set to take on a more public-facing role a là Michel Barnier. Frost delivered a speech in Brussels earlier this month and has taken a more active role of late on Twitter.

Oliver Lewis: The former research director in the Vote Leave campaign will serve as one of three deputy negotiators for Frost on the U.K. side. He was taken on in Downing Street as an EU adviser after Johnson became prime minister. He is across the detail and worked closely with Cabinet minister Michael Gove on no-deal planning. The other two deputies are government officials Lindsay Appleby and Matthew Taylor.

Other experts: Downing Street said relevant figures from across government departments would join the negotiations depending on which issues are being discussed. From the EU side, for every topic there will be someone from Barnier's team and someone from the relevant directorate general.

The most sensitive issues

Fish: Fisheries is one of the two conditions Michel Barnier has set for a trade deal with the U.K., the other being a level playing field to prevent anti-competitive behavior by Britain. Even though Europe’s fishing sector is economically fairly small, it’s one of the most politically sensitive topics in these negotiations. The initial draft of Barnier's mandate made fisheries one of the EU’s priorities, but EU countries still toughened the language in the final version. It now says that provisions must “uphold” existing reciprocal access, leaving barely any possibility for maneuvering during the talks. On the U.K. side, Johnson has long insisted Britain must become an independent coastal state and Michael Gove on Thursday ruled out using fishing as a "bargaining chip."

Level playing field: The EU wants Britain to sign up to its anti-dumping regulations, otherwise known as “level playing field rules.” It is worried that being so geographically close to the bloc, the U.K. could undercut its markets through state subsidies and the relaxation of environmental and labor laws, among other things. But Britain argues geographical proximity is irrelevant, and casts the EU as wanting to make it a legally subordinate country in the negotiations. Brussels has tied the level of market access to alignment on standards, so this will be a crucial tug-of-war in the talks.

The EU wants the Court of Justice of the European Union to retain its jurisdiction over areas of the future relationship that are born out of EU law or relate to security.

Governance: The EU wants the Court of Justice of the European Union to retain its jurisdiction over areas of the future relationship that are born out of EU law or relate to security. But the U.K. repeatedly says in its negotiating plan that it cannot accept any CJEU oversight. The Political Declaration — the text on the future relationship that accompanied the legally binding Withdrawal Agreement — says the CJEU could rule on interpretations of EU law. What the U.K. is willing to stomach will be a key point in the negotiations.

The method

Start: The first round of Brexit talks kicks off on Monday in Brussels and will end on Thursday. The exact agenda of this week is published here. Each round of U.K.-EU negotiations will be opened by the chief negotiators or their deputies and will also be closed by the top figures.

Location: Negotiators will switch between Brussels and London. This is a deliberate choice of the negotiating teams and marks a clear difference with the first phase of the Brexit negotiations, which took place exclusively in Brussels. It’s symbolically important that the U.K. and the EU now consider each other as equal interlocutors and hold negotiating rounds in both capitals — as is common in negotiations for other trade agreements.

How frequent will talks be? The EU and U.K. failed to agree on that question. Whereas Brussels wanted rounds lasting three weeks so it has a week for preparation, a week for negotiating and a week for debriefing EU capitals, the U.K. wanted to have rounds lasting two weeks. However, Brussels insisted it needs time to make sure everyone’s on board with the negotiations. They have now agreed that “full negotiating rounds will in principle take place every two to three weeks, unless agreed otherwise by the parties.” The dates for the rounds are set from now until May, with rounds from March 18-20, April 6-8, April 27-30 and May 13-16.

Order of business: At least 11 topics will be addressed at the same time. Given the short timeframe of the negotiations, the parallel discussions structure allows negotiators to proceed on different topics at the same time and assess later in which areas a deal is within reach within the timeframe and where more time is needed. The negotiating groups are trade in goods, trade in services and investment and other issues, level playing field for open and fair competition, transport, energy and civil nuclear cooperation, fisheries, mobility and social security coordination, law enforcement and judicial cooperation in criminal matters, thematic cooperation, participation in Union programs, and horizontal arrangements and governance.

Keeping everyone in the loop: Documents can only be made public with the consent of both parties. Given the EU’s complicated institutional framework, the Commission has built in steps to ensure its negotiators don't get too far away from their troops. For Parliament, David McAllister and the U.K. Coordination Group will be Barnier’s most important interlocutor. Brexit attachés from the different EU capitals will be updated via the Council’s Working Party on the U.K.

At some point in March, the U.K. government is expected to launch a consultation to work out the potential economic impact of its hoped-for trade deal with the EU.

On the U.K. side: Frost will report back to the government through the exit strategy (or XS) committee, which is chaired by Johnson and includes Chancellor Rishi Sunak, Foreign Secretary Dominic Raab, Cabinet Office boss Michael Gove and Attorney General Suella Braverman. Ministers have also promised to keep the U.K. parliament informed and allow MPs to scrutinize the process — although no specific commitments have been made.

Dates to look out for

March: At some point in March, the U.K. government is expected to launch a consultation to work out the potential economic impact of its hoped-for trade deal with the EU. But Downing Street made no commitment to publish the results. It is likely that a form of the assessment will be published, but it is also unclear as to when, leaving open the possibility that it could happen after a deal is agreed.

June: The two sides are set to hold a high-level conference in June to take stock of progress after the first few negotiating rounds. The U.K. has vowed to assess at that point whether the broad outline of a deal is clear and and deliverable in the subsequent few months. If not it could shift focus, ditch the negotiations and focus on ending the Brexit transition period without a trade deal. The two sides must also decide by July 1 whether to extend the transition for up to two years (the U.K. has ruled out an extension) and there is a June deadline for a fish deal too.

September: In its negotiating plan document, the U.K. said it would want a deal “capable of being rapidly finalized by September” to press on with talks after June.

Mid-October: The EU aims to wrap up negotiations by the mid-October European Council summit, according to an earlier timeline presented to reporters. Brussels hopes that the time left between then and the end of the year will be sufficient to ratify the future agreement. But that depends on whether the EU has to involve national parliaments. If not all parts of the deal are of exclusive EU competence then EU countries can demand that their national (and some regional) parliaments must have a say.

December: The transition period ends on December 31 and the U.K. has insisted it will not be extended. Johnson says he would prefer to leave the bloc without a trade deal than face stretching the process into 2021. “This leaves a limited, but sufficient, time for the U.K. and the EU to reach agreement,” the U.K. negotiating plan says.

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