If we walk away from our international obligations (say not paying the EU exit bill), I wonder how much other countries will trust us in the future when it comes to trade agreements.
Even setting aside the issue of WTO tarrifs when trading with europe, what about the rest of the world? Our membership of EFTA means we currently benefit from tariff free exports to the following countries
Albania, Bosnia-Herzegovina, Canada (Canada-European Free Trade Association Free Trade Agreement), Central American States (Costa Rica, Panama), Chile, Colombia, Egypt, Gulf Co-operation Council (Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, United Arab Emirates), Hong Kong (China), Israel, Jordan, South Korea, Lebanon, Macedonia, Mexico, Montenegro, Morocco (excluding Western Sahara), Palestinian National Authority, Peru, Serbia, Singapore, Southern African Customs Union (Botswana, Lesotho, Namibia, South Africa, Swaziland), Tunisia, Turkey and the Ukraine
Not to mention those we're currently in discussion with in Algeria, Central American States (Guatemala, Honduras), India, Indonesia, Malaysia, Russia / Belarus / Kazakhstan, Thailand and Vietnam.
We throw all those away at the end of March 2019, even if we agree a deal with EFTA. Even if we get a great deal, which of the 46 other countries listed above are top of the list for negotiations starting April 2019?
Canada took about 8 years to come to an arrangement with europe, 9 years for Canada-south korea, 9 years Canada-Colombia, so we could expect a deal with them as soon as 2027.
South Korea took a mere 6 years to come to agreement with Peru, so if we prioritise them we could have one in 2025 - before HS2 opens!
China-South Korea is unusual, it took under 4 years to complete, and with that timetable we should be grilling by Christmas 2023.