Prime Minister Theresa May has triggered Article 50 of the Lisbon Treaty nine months after the UK voted to leave the European Union.

In a letter to the European Council president Donald Tusk, May signalled the start of the nation's departure after joining the European Economic Community on New Year's Day, 1973.

Today is the end of the beginning.

Now the real Brexit process begins. The phoney war is over.

Here is what will happen next:

European Council president Donald Tusk will issue a draft proposals on how the remaining 27 EU nations should conduct the negotiations with the UK.

In a statement released today, the Council said: "These guidelines will set out the overall positions and principles in light of which the Union, represented by the European Commission, will negotiate with the United Kingdom."

The guidelines will be adopted by the remaining 27 nations on April 29.

The political leaders of the European Parliament have drafted a resolution setting out what the continent's MEPs want to see from Brexit.

MEPs will then vote on this resolution in early April.

The resolution calls for the UK to be denied access to financial passporting after it leaves the EU and other benefits that come with membership.

It is also calls on Europe's negotiators to ensure there is no desire to see a 'hard border' between Northern Ireland and the Republic of Ireland.

The negotiations should begin with securing the rights of EU citizens in the UK and British citizens living in the remaining EU bloc, the resolution argues.

First Minister Nicola Sturgeon will approach Downing Street to negotiate towards holding an independence referendum between autumn 2018 and spring 2019.

The UK Government says it is not interested in starting talks before the UK leaves the EU.

What happens next then?

Sturgeon says she will go back to Holyrood after the Easter recess and set out the next stage.

She told MSPs on Tuesday: "I hope that the UK government will respect the will of this parliament.

"If it does so, I will enter discussion in good faith and willingness to compromise.

"However, if it chooses not to do so, I will return to parliament after the Easter recess to set out the steps the Scottish Government will take to progress the will of parliament."

The heads of Europe's governments will meet to discuss Brexit later next month.

All of the EU's presidents and prime ministers will be there except one: Theresa May.

As mentioned previously, the Council will meet to set its "guidelines" for the negotiations ahead.

This will be seen as the nations of the EU setting the political direction of the Brexit deal.

Although, technically, they speak as one voice and one organisation each has their own national interests which they want to gain from the exit deal.

Ireland, for example, wants no custom checks on its border with the European Union while nations such as Estonia are keen to retain as much security cooperation as possible.

European Union officials and their British counterparts will start preliminary discussions from today.

The main discussions are not expected to begin until May or June, after the French presidential elections.

There will also be a possible interruption in September when German voters go to the polls.

Germany is most powerful player in the EU. Who is in power in Berlin and what they want to see from Brexit is likely to define what the exit deal looks like.

We are likely to see our first political row, however, fairly swiftly after talks begin.

The European Union wants to sort the terms of divorce, including a hefty bill for Downing Street to pay, first before agreeing its future trading relationship with the UK.

Downing Street wants to do both simultaneously.

Theresa May has threatened to walk away from the talks with no deal at all unless she gets a future arrangement sorted and one which she likes.

The EU's chief negotiator, Michel Barnier, has set out his preferred deadline for the deal.

Speaking in December, he said: "Should the UK notify the Council by the end of March 2017 [triggering Article 50], as Prime Minister Theresa May said she would, it is safe to say that negotiation would start a few weeks later and an Article 50 agreement be reached by October 2018."

From there we turn to Britain and Europe's politicians for the next stage.

The European Parliament and the British Parliament will vote to approve or disapprove the final Brexit deal.

When they get to actually cast their votes is not clear yet. It depends, mainly, when the deal is finalised.

'What happens if either parliament rejects the deal after the months of negotiations?' I hear you ask.

No one knows.