I was wondering if Dunkirk remains English somehow* how hard would it be to create a Channel Tunnel from Dunkirk to England? Would it be too expensive to contemplate. Would it be possible, but just at a later time (early 21st century)?
If Dunkirk would be technically possible, what would be too far away. Would a channel tunnel from the current Belgian border to England be possible? How far can we go before it becomes ridiculous? Bruges, Rotterdam, Hamburg?
*Or if Dunkirk becomes Belgian or Dutch or whatever and relations between France and England/Britain go/remain sour