That security guarantee to Poland turned out quite expensive in the end.

You know, if you put it this way, it's really a miracle that britain as an independent country still exists at all, that it's not been conquered from the continent since 1066, and that has been in no small part thanks to a british foreign policy of making sure that no country in europe becomes so dominant that they might take on britain, a foreign policy which included that security guarantee to Poland.

Which was the type of unforced error that almost brought together the Molotovian facist-communist tagteam that almost destroyed the entire world.

And Poland got occupied anyway. Truly Metternich-level stuff.