Brexit is one of the most complicated affairs in policy. Dozens of trade treaties have to be renegotiated. Tens of thousands of pages of European law have to be replaced. And, of course, Britain wants to work out a custom deal with the European Union whereby, in essence, the island gets all the benefits of being in the EU — trade, especially — without any of the drawbacks — paying money, having to give up sovereignty. This is where, on top of the mind-boggling technocratic complexity, the politics come in.