>In the long run, Britain will always tend to ally against the dominant continental power.
Without that, the modern era would probably never have happened. That is because one state would have probably converted Europe into an empire, dominated by a single culture and religion, instead of the great competition of ideas and technologies that happened because there were so many independent states.
One could argue that the Europe of the many states only lead to the horrors and suffering of the world wars, while a multiculturaly diverse but politicaly uniform Europe, built by, say, Napoleon, could have been a United States of Europe. Not being a bunch of countries inflicted so many different nationalisms has worked pretty nicely for them.
Without that, the modern era would probably never have happened. That is because one state would have probably converted Europe into an empire, dominated by a single culture and religion, instead of the great competition of ideas and technologies that happened because there were so many independent states.