28/03/2017 03:54 BST | Updated 29/03/2018 06:12 BST

'Nothing Is Agreed Until Everything Is Agreed' - The Monumental Task Is Ahead

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The moment is finally upon is: Theresa May will trigger Article 50 on Wednesday, marking the beginning of the UK's departure from the European Union.

It is both coincidental and ironic that Brexit will formally commence at a time when the EU is celebrating the 60th anniversary of the signing of the Treaty of Rome. The Treaty marked the first step on the road to political and economic integration on across the continent, a journey which the United Kingdom was at first reticent to embark upon and will now be the first to step away from. Whilst acknowledging the complex issues which have led to Brexit, EU leaders have outlined their commitment to fight for the Union's long-term future. There is a growing anti-EU feeling in many countries, including rising doubts about the future of the single currency in Italy and Greece in particular. Self-preservation will be the EU hierarchy's number one objective throughout the Brexit process.

Neither the UK nor the EU will be naive to the monumental task that lies ahead. The situation is unprecedented and has already been marred by legal battles in London and Dublin. The time period for negotiations - set as just two years under the terms of Article 50 - is also widely seen as optimistic at best and impossible to achieve at worst. Negotiations are made much more complicated by the fact that we actually have to strike two deals. The first is 'divorce settlement' that will set out the terms on which we leave the Union. This alone will be hugely contentious, with the EU claiming we could leave with a bill running into the tens of billions of euros to cover our existing debts and obligations. There will also be disputes about our role in a number of EU agencies and initiatives. Will we remain part of the OpenSkies agreement that allows British travelers to fly across Europe with ease? Will students still be able to use the Erasmus programme to go and study abroad? Many uncertainties remain.

The second goal is a free trade agreement defining our new relationship with the 27 remaining EU countries. The negotiations will again be hugely complicated as we attempt to create a new, 'bespoke', customers, tariffs and border arrangement with our former EU colleagues. However the talks themselves are just the first hurdle. Any trade deal will need to be ratified by parliaments across Europe as well. Analysis by Nick Clegg has found that the fastest ratification for any 'mixed agreement', resolving customs and trade issues at the same time, was two years. This was for an agreement with Moldova. A deal with the UK will be infinitely more complex.

The journey to Brexit is going to be long and complex and Theresa May's triggering of Article 50 this week is just the first step. There are a myriad of decisions to be made, issues to be resolved and personalities to manage. With the key players agreeing that "nothing will be agreed until everything is agreed", it is clear that the situations will be in flux until the very last moment.

To help make sense of the Brexit process and the many questions that are still to be answered, Four Public Affairs has produced a 'Guide to Brexit' mind map. This shows some of the ever-expanding web of issues now engulfing the Government. There are decisions to be made. What Theresa May and David Davis choose to give away and what they choose to keep will impact British businesses and lives for decades to come. The stakes could not be higher.