Of course it will happen, simply because there is no alternative. The whole U.K. assumption that A50 can simply be revoked if the U.K. government changes it's mind is nonsense. There is no procedure on the EU side to accept it - who would have the authority to accept it? The council, the commission, the parliament, all three? And it is always open to the ECJ to hear a case on a treaty breach taken by a concerned citizen (UKIP member perhaps) to have the treaty terms enforced.

No BREXIT will have to go ahead even if it is to satisfy the technical requirements, the question is what happens after that.

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"There is no passion to be found playing small - in settling for a life that is less than the one you are capable of living." - Nelson Mandela