It’s official: The UK has, finally, started the process of leaving the European Union. British prime minister Theresa May signed a letter in London and sent it to the European Council in Brussels for delivery today, formally invoking Article 50 of the Lisbon Treaty.
Article what of the what? Article 50 is a passage in the constitutional documents that govern the EU, explaining the procedure for a member state to exit the bloc. It is short and vague, since the drafters never thought it would actually be used. But here we are, nine months after British voters opted for Brexit, launching negotiations for what could be a messy divorce.
One of the few things that Article 50 is clear about is the timeline: EU rules no longer apply in the departing country “from the date of entry into force of the withdrawal agreement or, failing that, two years after the notification.” Divorces are rarely easy, and breakups after more than 40 years—the UK joined the EU in 1973—are especially fraught. Most expect the negotiations to take the full two years (and possibly longer, if all agree to extend the deadline).