You have to deal with the de facto leaders of any country.
That's just the real world. Chamberlain had to deal with Hitler. Because Hitler was the leader of Germany at the time. The fact he was a complete **** was irrelevant
One of the reasons I would prefer the UK to be in the EU is that I don't want the country to be a lackey of the USA. De Gaulle had the right idea when it came to America. Our common language is a huge disadvantage. They are not 'us'. They are not even our mates when it comes down to it. They are the source of all the political shite that transfers over here - monetarism, populism, libertarianism, neo-liberalism - you name it. Now we will have that turd Farage playing mini-me Trump, and people will fall for it - again!