To answer questions about trade with data (rather than pulling figures out of…let’s say thin air), I’ve put together a thread on the facts (trade for 2017; goods only*):

How much UK trade is:
1. “On WTO RULES”?
2. On WTO rules ALONE?
3. On WTO TARIFFS?

4. What’re the details? 1. How much UK trade is “on WTO RULES"?
Short answer: All of it

UK is WTO member
All trade with other members is bound by WTO rules
They are basic rules of trade, but, through EU, we have trade deals/arrangements with ALL WTO members & some non-members that go beyond basic level