"Leaving aside the rights and wrongs of Brexit, purely in terms of negotiating technique, it is an object lesson in how not to do it. As the bluster and self-congratulation dies down, it is worth standing back and looking at what we can learn from the debacle." 

The quote is from the attached article in European Politics and speaks for itself. The British voted for Brexit on the basis of  a dream, their governments turned their dream into a negotiating nightmare for all concerned and finally ended with a bad deal.The pre-christmas deal is a "first"! That is to say a first ever trade agreement made to make trade more difficult, worse and more cumbersome than what existed. All of it in the name of a stupid dream of so called sovereignty, version 19th. century.