It is not this that I promised to do. From EU referendum blog, this legal precept seems to go straight to the nub of the feeling across thre United Kingdom when one considers the European Union. Essentially we were sold a false bill of goods.
The Key aspect seems to be,
The modern formulation of the doctrine of frustration can be found in the decision of the House of Lords in Davis Contractors Ltd. v. Fareham U.D.C, since 1956. Lord Radcliffe stated that:
…frustration occurs whenever the law recognises that without default of either party, a contractual obligation has become incapable of being performed because the circumstances in which performance is called for would render it a thing radically different from that which was undertaken by the contract. Non haec in foedera veni. It was not this that I promised to do."