The Brexit referendum in June laid bare deep divisions in British society, which are still in evidence today. Much of the tabloid press, which has opposed the EU for years, celebrated Wednesday's move. The Daily Mail's headline read simply "Freedom," while the Sun projected the words "Dover and Out" onto the iconic white cliffs of Dover.

But not everyone shares this jubilation. "I feel as if I am watching my country plunge into the abyss," says Louise Jones, a London-based remain voter. "No one knows what is going to happen next, or even how the negotiations should work. This will most likely result in a major economic hit and also, quite possibly, the breakdown of the UK itself. I think public opinion will change once we start to feel the effects - increased cost of living, expensive holidays, to name just a few, "she told DW.

Read: Long road to Brexit: the UK triggered Article 50, but what happens next?

A poll by YouGov ahead of the historic move found that a majority of Britons (69 percent), including remainers, now support the government in getting on with leaving the EU. However, a majority also believe that Britain can retain access to the single market while controlling immigration, despite consistent warnings from senior European leaders that the two are mutually exclusive.

Unclear path

No nation state has left the European Union before, and the instructions for doing so are brief. Article 50 allows two years for negotiations, which most experts agree is not sufficient. "The two sides are at considerable distance given the short time they've got to converge - over the departure bill, access to the single market, the rights of EU citizens," says Matthew Cole, lecturer in history at Birmingham University. "That two year timetable was not designed by people who ever envisaged it being followed. Article 50 was not made with the expectation it would be used by a major member state like Britain in the near future, so it's not surprising that it's not entirely realistic," he told DW.

The question is who will be having the last laugh?

It recently took seven years for a trade deal to be agreed between the EU and Canada, a far simpler negotiation. At present, even the sequence of negotiations are up for debate: it is unclear whether the EU will discuss the terms of a future deal alongside the "terms of divorce," as Britain wants, or wait to sort out the terms of exit before discussing the future.

Read: EU has strong Brexit negotiating position, says German Foreign Minister

The immediate issues to address include money that Britain owes the EU, and the fate of EU nationals in Britain and British nationals in the EU. "I'm afraid about what the future holds for me. I've built a life here over the course of seven years, and I don't know if I will be allowed to stay," Marie Bernard, a French citizen based in London, told DW. "It's a frightening time and I, and the 3 million other Europeans in the UK, would like some clarity as soon as possible."

Now that Brexit has moved from the realm of the theoretical to the practical, Prime Minister Theresa May faces a new set of challenges. "Until now, it's been relatively easy for her. All she's really had to do is keep her own party and the media in the UK happy," says Oliver Patel, researcher at University College London's European Institute. "Now she is officially negotiating with 27 other countries with their own interests, priorities and red lines. The challenges lie in making concessions and compromises to the EU and also selling them to people back home."

Read: 'Kick in the teeth' for EU nationals in the UK

Disunited kingdom

The uncertainty over the future is not restricted to negotiations with Brussels. Within the UK, Scotland is lobbying for a second independence referendum. Meanwhile, there is a question mark over what will happen to the border between Northern Ireland and the Republic of Ireland. It is currently open due to the Good Friday peace agreement, but may have to be re-instituted if the two nations have different customs arrangements.

"Two of the UK's countries are in very challenging positions with their relationship to the center," Patel told DW. "This comes at the same time as Brexit begins, probably the most challenging and complex thing to happen to the country for decades. It undermines the notion of a stable British state that was received wisdom for many years."

Read: Scottish nationalists take on London over Brexit

Some commentators in Britain have questioned the timing of today's move, given that two major European powers - France and Germany - will be looking inwards for their own national elections, further reducing the negotiating time.

Yet all are agreed on the scale and complexity of the task ahead. "This has got to rank alongside Versailles as a negotiation that affects not only Britain but the balance of power in Europe, the nature of the EU, the future of the EU," says Cole. "May will be also be dealing with potential challenges at home, in Scotland and Northern Ireland. She has set herself a task greater than almost any PM since World War Two. It's an ambitious target."