Different trade barriers. The EU already has very few tariffs, most of them strategic. The weighted mean applied tariff rate for EU member states is 1.57% [1].

Different trade barriers. The EU already has very few tariffs, most of them strategic. The weighted mean applied tariff rate for EU member states is 1.57% [1]. The tricky aspect of free trade agreements is the non-tariff barriers [2]; those relate mostly to regulations, including labor protection, health, the environment, money laundering, and such. They are very difficult to negotiate, because a lot of them are not about economics, but about things that people genuinely care about. For example, one of the major sticking points with TTIP was food quality (the chlorinated chicken debate). As a result, trade agreements that want to reduce regulatory barriers take years to negotiate. Within the EU, this problem is addressed by having an actual, full-blown bicameral legislature and a court of justice to protect the interests of the member states and their citizens. But the UK doesn't even like the ECJ, so this is not going to be easy. As far as the negotiations go, the British government has nobody but itself to blame. It doesn't even seem to be prepared for negotiations (and one has to wonder what it wasted the past year on); it has consistently and aggressively talked trash about the EU (in order to appeal to UKIP voters?), has issued threats (such as turning the UK into a European Singapore), and so forth. It should not be surprising that the reaction hasn't exactly been amicable. [1] http://data.worldbank.org/indicator/TM.TAX.MRCH.WM.AR.ZS?view=map http://data.worldbank.org/indicator/TM.TAX.MRCH.WM.AR.ZS?vie... [2] https://en.wikipedia.org/wiki/Non-tariff_barriers_to_trade https://en.wikipedia.org/wiki/Non-tariff_barriers_to_trade