When the SS Ancon became the first ­seagoing vessel to transit the Panama Canal, on August 15 1914, the ­celebrations were muted – world war had just broken out. But the significance of the event was clear: the canal offered a northern-hemisphere route that could accommodate every ship then afloat.

That has since changed. While all the container ships in service before 1990 could fit through the canal’s locks, nearly half those on order now are too large. And the canal is clogged with vessels: those that have not booked long in advance must often wait four days to get through.