I checked again and I am sorry to report that the famous UK headline “Fog in Channel; Continent Cut Off ”actually never appeared. Not in the Yorkshire Post before World War I, nor in the 1957 Times, or anywhere else. Unfortunately, as Boris Johnson would say, it’s apocryphal.
The fact that it is such a persistent urban myth, however, speaks for Anglo-centric attitudes up to our time. Understandably, the British were obsessed with the consequences of Brexit for Britain (albeit with increasing boredom); You seem to be less concerned about what this will mean for the European Union.