3. The Treaties shall cease to apply to the State in question from the date of entry into force of the withdrawal agreement or, failing that, two years after the notification referred to in paragraph 2, unless the European Council, in agreement with the Member State concerned, unanimously decides to extend this period.

Two years is the maximum period for negotiations unless extended by unanimous vote. There is no minimum. The UK could write a letter to the EU Council seeking to withdraw on 1/1/2018 and if the Council agreed to this, that agreement could constitute a withdrawal agreement within the meaning of A. 50.3. Article 50 is not prescriptive as to what a withdrawal agreement must contain. It could be little more than a glorified mutual Auf Wiedersehen.

But I agree, this scenario is somewhat far fetched. I raise it only to illustrate how rapidly the current unstable situation could spin out of control with mounting acrimony on both sides. Both sides are still shouting past each other with little sign of any gathering consensus - even on the UK side alone. If the united EU27 front crumbles, all hell will break lose. The stakes are high and getting higher with every ratcheting up of the rhetoric.

Index of Frank's Diaries