What time will the headlines cross?
Short answer: We don't know but by noon or 12:30 pm in London at the latest.
Long answer:
We know that it will be tomorrow (Wednesday, March 29, 2017) because that's what Theresa May has promised. But we don't know exactly when we will get the announcement.
What we do know is the Article 50 process. All it means is that May will inform the European Council of Britain's intention to leave the EU.
The actual text of Article 50 in the Lisbon Treaty:
1. Any Member State may decide to withdraw from the Union in accordance with its own constitutional requirements.
2. A Member State which decides to withdraw shall notify the European Council of its intention. In the light of the guidelines provided by the European Council, the Union shall negotiate and conclude an agreement with that State, setting out the arrangements for its withdrawal, taking account of the framework for its future relationship with the Union. That agreement shall be negotiated in accordance with Article 218(3) of the Treaty on the Functioning of the European Union. It shall be concluded on behalf of the Union by the Council, acting by a qualified majority, after obtaining the consent of the European Parliament.
3. The Treaties shall cease to apply to the State in question from the date of entry into force of the withdrawal agreement or, failing that, two years after the notification referred to in paragraph 2, unless the European Council, in agreement with the Member State concerned, unanimously decides to extend this period.
4. For the purposes of paragraphs 2 and 3, the member of the European Council or of the Council representing the withdrawing Member State shall not participate in the discussions of the European Council or Council or in decisions concerning it.
A qualified majority shall be defined in accordance with Article 238(3)(b) of the Treaty on the Functioning of the European Union.
5. If a State which has withdrawn from the Union asks to rejoin, its request shall be subject to the procedure referred to in Article 49.
So all the text really says is that they need to "notify the European Council of its intention" to leave the EU. Practically, May will do that by sending a letter to EU Council President Donald Tusk. That's what happens on Wednesday.
Now for the to-the-minute timing
There are 24 hours in a day and theoretically, May could choose any of them but we have a few clues.
The Guardian reports that Sir Tim Barrow, the UK's permanent representative to the EU, will deliver a letter triggering article 50 talks at 12.30pm on Wednesday but I expect May to announce it earlier.
The time I will be watching most-closely is early in the UK morning. If I had to guess an exact time, it would be 7 am in London (that's 0600 GMT), 2 am in New York and 3 pm in Tokyo.
Governments like to make announcements first thing in the morning, so it's over and done with. That leaves plenty of time for the spin, questions and formalities. It also takes away the uncertainty of the timing before people start watching the clock. It would also be done before the local market opens.
At latest, I'd expect it by noon in London because that's when May is scheduled to be in parliament for the Prime Minister's Question Time and the government has said she will inform parliament of Article 50. Once she starts speaking, or even when she arrives in parliament, you can assume why she's there.
How the news crosses is a bit of mystery. It's not like some magical thing happens when she sends the letter and reports will cross. I'd expect the Prime Minister's staff to post a notice along with a statement before going to parliament because that's the tightest way to control the message.
In short, there isn't necessarily a 'trigger' in a sense. A letter will be drafted, revealed, spun and delivered. Which one the market takes as the 'declaration' isn't necessarily relevant.
What to watch next
A barrage of statements are surely already sitting on desks and waiting to be sent out. For instance, Francois Fillon already inadvertently sent his.
One that's already scheduled is from Donald Tusk. On his agenda is a press statement no the UK Article 50 notification. It's listed at 1:45 pm local time in Brussels. That's 12:45 pm in London.
Opposition parties in the UK and counterparts in the EU know what to expect and know what they want to say in response. There will be many headlines crossing in the hour or two that follows but unless there is some inflammatory rhetoric, it will probably be ignored.
As for trading the decision in the forex market. Watch this video for real-time strategy.
