In the end, the letter that triggered Brexit was neither long nor short, neither fair nor foul. It restated several things we already knew about what Prime Minister Theresa May was seeking and planning — the U.K. will leave the single market, for example — but brought in new intricacies, such as an explicit desire to include financial services in any future trade deal, and some not-so-veiled threats over the issue of continued security cooperation.  How will it all pan out? We’ll follow every step of the way. In any case, we should have an answer by March 29, 2019. A letter from London: The moment nine months in the making came at around 12:20 p.m. in London when Tim Barrow, the U.K. envoy to the EU, handed EU President Donald Tusk a letter invoking Article 50 of the Lisbon Treaty. Two years of talks over a divorce deal and potentially a new trade pact will now follow. What did the letter say? May struck a conciliatory tone, calling for the upcoming negotiations to be conducted “constructively and respectively” and saying she wanted the bloc to “succeed and prosper.” Her warm words were matched by those in the EU, with Tusk expressing hope that the U.K. would be a “close partner.” What does she want? The U.K. is seeking the political version of a friendly divorce. May wants to also nail down a sweeping free trade deal that encompasses finance, a key part of the U.K. economy. An immediate clash: While May again pitched for talks on the divorce and trade deal to take place in tandem, Tusk drew a line by insisting the “orderly withdrawal” must be the initial focus. The European Parliament took an even harder line in arguing that “the U.K. must honor all its legal, financial and budgetary obligations.” Money talks: Although May said the U.K. would cover some of its financial commitments, May hinted Britain would also make claims on its share of EU assets. “We will need to discuss how we determine a fair settlement of the U.K.’s rights and obligations as a departing member state,” she said. A hint of menace: May said a collapse in talks and the imposition of tariffs on U.K. exports to Europe would carry security implications for the bloc as the joint fight against crime and terrorism would be weakened. She reminded her counterparts that regional “security is more fragile today than at an time since the end of the Cold War.” That did not go down well on the continent. “Security is far too important to start to bargain it against an economic agreement,” said Guy Verhofstadt, the European Parliament’s representative on Brexit matters. The business backdrop: The U.K. government is almost alone in thinking it can nail down a trade deal within two years, but May opened the door for a longer period by saying she wants “to avoid any cliff edge” for business. The pressure from industry built on Wednesday as carmaker Ford lobbied for tariff-free trade and Ryanair worried about losing access to the continent. JPMorgan Chase said it will “inevitably” have to move some staff from London. What next? Having had to wait for the U.K., the rest of the EU now controls the clock, and the two years on it are already ticking down. Tusk will release draft guidelines for negotiator Michel Barnier by the end of Friday, but leaders won’t get around to ratifying them until April 29. Proper engagement may not even take place until after France’s elections. People you’ve never heard of are going to be negotiating Brexit. With the letter out of the way, it’s time for the talks to begin. We know that U.K. Brexit point man David Davis is going to lock horns with his EU counterpart Barnier. But who are the other key players, the civil servants and the senior officials who will do the water-carrying and the late-night haggling?