Negotiations with the EU will begin formally as soon as the Article 50 trigger is pulled. But these negotiations will struggle to get going before autumn 2017, and will have to conclude by autumn 2018.
Of course, there is no rule-book for these negotiations and few informative precedents. But given the EU’s likely process once Article 50 is triggered, we can begin to set out a potential timeline. Naturally, anything from the French and German elections, to UK politics could push things off course. The key point is that this timeline leaves just 12 months for substantive negotiations.