The most difficult part of Brexit will be to figure out the trade regime between the U.K. and the rest of the E.U. because the level of trade integration between the members of the E.U. is the deepest in the world and integrates regulations that govern how products and services are produced and sold within the E.U.
The fact is that during the post-1989 heyday of globalization optimism, political and business elites did not think enough about the prospect - plainly predicted in economic theory - that trade would harm some people even while leaving society as a whole better off. The result was overpromised benefits and inadequate adjustment plans.