They wouldn't be starting the trade war, the war has already begun. The Europeans are threatening to impose tariffs on British goods unless Britain signs up to

They wouldn't be starting the trade war, the war has already begun. The Europeans are threatening to impose tariffs on British goods unless Britain signs up to EU rules. Threatening to respond in kind is completely reasonable. Whatever the rules of the EU were is totally irrelevant now, except insofar as they represent interests that the EU is seeking to defend. This is now a negotiation between sovereign powers, each with leverage over the other. As to whether Britain can win, I think the next Conservative government is likely willing to walk away from the table. Shifting to a more Atlantic-oriented vs. European-oriented position would be a somewhat painful economic transition, but it's what a lot of Tories want at heart anyway, so it's not an infeasible outcome if the continent proves unyielding. And don't forget that Merkel and Hollande cannot afford to be seen allowing hundreds of thousands of job losses in some effort to punish Britain and deter the further crumbling of the EU, which is increasingly unpopular in their countries as well. Alternative for Germany (AfD) and the National Front (FA) are biting at their heels, and FA might actually win the presidency in France next year, which would almost certainly be the end of the EU.