British Prime Minister Theresa May will trigger Article 50 of the Lisbon treaty by sending a seven-page letter to Donald Tusk, the president of the European Council, on Wednesday. The EU's response comprises two steps -- so-called "guidelines" agreed by EU leaders and a more detailed legal "negotiating mandate." It could take until September for the EU to decide its opening position before talks with Britain can begin. Michel Barnier, the European Commission's Brexit negotiator, could further stall the negotiations by demanding a "divorce-first" approach, delaying talks on a future trade deal until Britain has agreed principles on an exit bill and the rights of EU migrants. This dialogue could last until the end of the year. The terms of exit, the transition deal, will be negotiated between the remaining 27 EU member states, each of which has a veto. It will also be subject to ratification in national parliaments, meaning, for example, that Hungarian lawmakers could scupper the deal.
