361 days ago, Britain went to the ballot box to decide whether we should be the first member state to leave the European Union. 52 per cent of those that turned up chose to leave.

Today is the first official day of divorce proceedings, after 44 years of rocky marriage. And like any break-up, it’ll be messy.

What’s happening today?

The first talks began at 10am at the EU Commission in Brussels. We don’t expect much substance. The focus for today will be on the “terms of reference” – what is and is not on the agenda, how often they’ll meet, and in what order key issues will be discussed. Today’s meetings will be talks about talks.

There’ll be a joint press conference this evening from both sides. We can expect more of the conciliatory language we heard from Davis and Barnier this morning. (Take a drink every time you hear the words “partnership”, “constructive”, and “friends”).

Who’s on Team Brexit?

The UK’s negotiating team will be led by Brexit Secretary David Davis, who campaigned for Leave in last year’s referendum. At the time, he claimed that the EU “has been in decline for some time”, describing it as “a crumbling relic from a gloomy past“.

He’s had to soften his tone since then, publicly at least, and said today that he is “determined to build a strong and special partnership” with what he calls the UK’s “allies and friends” in Europe.

His deputy is Olly Robbins, the most senior civil servant at the catchily-titled Department for Exiting the EU. A former official at the Home Office, he’s familiar with some of the trickiest issues facing Brexit negotiators on both sides – including immigration and border security.

We don’t know much of Robbins’ personal views on Brexit. Quite right too, as he’s a civil servant. He’s been praised for his non-partisan approach in the past, including by Labour peer and former minister Tessa Jowell, who described him as “very popular” and someone who embodies “the essence of the impartial civil servant”.

Robbins will be joined at the negotiating table by fellow civil servant Sarah Healey, who’s director general at the Brexit department.

Finally, representing the UK in the Brexit gladiatorial ring, we come to Sir Tim Barrow, the UK’s ambassador to the EU. He was rapidly installed into this key role after his predecessor, Sir Ivan Rogers, resigned last year, urging his colleagues to challenge the “ill-founded arguments and muddled thinking” of those in power.

Barrow’s appointment divided opinion among prominent Brexiteers, drawing praise from Boris Johnson and frustration from Nigel Farage(although Farage’s beef might be that he didn’t get the gig himself).

What is the government’s position on the big issues?

Immigration

We’ve had mixed message from the government on this. The recent Tory manifesto said that “leaving the European Union means […] that we will be able to control immigration from the European Union” and that the government will “reduce and control the number” of EU migrants to Britain.

But earlier this year, Theresa May seemed to suggest that free movement of EU citizens into the UK could continue for a time after we officially leave the EU in 2019. Indeed, the Prime Minister said in April that she “cannot guarantee” that migration levels will fall after Brexit.

Part of the reason that immigration will be so difficult is because it’s closely linked to…

Membership of the single market

Membership of the single market allows the free movement of goods, services, money and people between the countries that are part of the arrangement.

If you’re in the single market, your citizens can live and work in any of the 32 member countries, but it’s not the same as having open borders. You still need to get your passport checked before you can come into the UK. That won’t change whether we stay in the single market or not.

In January, Theresa May said that the UK will leave the single marketbecause staying in it would mean “not leaving the EU at all”. But that is probably not the only reason – or even the main one. It’ll be almost impossible for the Tories to meet their commitment to reduce migration from the EU if the UK stays in the single market.

Germany’s foreign policy spokesman Jurgen Hardt has said that being part of the single market and restricting free movement of people is “not a realistic option”.

So despite Boris Johnson’s infamous statement that his policy on cake is “pro having it and pro eating it”, that may not be the way the cookie crumbles.

And in a further culinary flourish, German Chancellor Angela Merkel has made clear that the UK cannot “cherry pick” the terms of its Brexit deal when it comes to single market access.

The message from Europe is clear: you can’t be in the single market if you restrict immigration from the EU.

What happens if Theresa May stops being Prime Minister?

The Prime Minister said she called the election to secure the parliamentary mandate she needed to get the best deal for Britain in Brexit negotiations.

She’s just about held onto her job, but the results of this month’s poll have – by her own logic – put her in a worse negotiating position than when she started. Her parliamentary majority is lost, and her personal credibility is under attack.

There are a few ways she might leave Downing Street – a Tory leadership coup, the collapse of the parliamentary deal with the DUP, or simply public pressure forcing her out.
It’s very difficult to tell what that would mean for Brexit.

Technically speaking, a new tenant in Number 10 wouldn’t derail Brexit talks. But it could shift the balance of power between the UK and the EU – especially if a new Prime Minister took office with a significant parliamentary majority for a specific vision of Brexit.

Can we go back on Brexit?

New French President, Emmanuel Macron, ruffled feathers on this side of the Channel last week by reminding Theresa May that “the door remains open” to Britain if it wants to remain in the EU.
But legal opinion is split on whether that would be possible. The UK has triggered Article 50 of the Lisbon Treaty, which formally begins the process of departure. There’s nothing in the law itself that says whether it can be revoked or not.

Lord Kerr, who drafted the text of Article 50, says that it could be reversed if the UK chose to. However, the UK Supreme Court said in its recent judgement on Gina Miller’s Brexit challenge that it accepted “as common ground” that “once given [Article 50] cannot be withdrawn”. But that still hasn’t been formally put to the courts.

In either case, it’s unlikely to be tested, given the political ramifications.