The Dachau gatehouse sits four-square amid a tall stone wall fronting the vast compound, an immense pseudo-gothic baronial interpretation, built by inmate labour. From that frontage one might be forgiven for thinking one was entering a royal palace or arch-ducal hunting lodge. Once through the gates the fantastic illusion vanishes instantly, replaced by a grey dusty wasteland of courtyards, low office buildings and concrete blockhouses. New inmates don’t arrive this way; it’s far too ceremonial, would give them far too great a sense of their own importance; instead they mostly arrive in open goods trains that pull into specially constructed sidings on the far side of the compound, sidings modelled after the great stockyards of Chicago, which open directly onto the inmate sorting and containment areas.

Functionally the sidings and their attendant buildings are strangely similar to any great airport around the world today: designed to sort and funnel large numbers of people into the right areas with the least possible waste of time or space.

Over the centuries much of Europe north of the Alps has almost become accustomed to handling large movements of people, refugees from war, pestilence or drought, and even the odd few thousand crusaders are – if not a familiar sight – then an understood and recognisable sight. The knowledge of how to deal with such influxes is now deeply buried in the psyche of most places and peoples of central Europe.

From the days of Charles Martel on through the middle ages into the early modern era of the mid 19th Century such movements were almost regular events: the last great historic movement followed the second war in 1945 and ’46, mostly from east to west, although perhaps the modern economic migrations following the collapse of the Soviet Empire and the reunification of Germany come close. Today, Europe is seeing an almost equal swarm of economic migrants from Africa and elsewhere. For the most part European invasions and campaigns followed the major river roads or the major transecting roads: the rivers of northern Europe mostly run south to north – from the mountain spines to the Baltic and the North Sea. The transecting roads run mostly east-west, connecting the major towns on the rivers, following the lowlands where possible, and over the easiest of the mountain passes when not. The routes have been there for millennia now, well established and well known, connecting Lyons and Paris to Augsburg and Nuremberg to Prague and Kiev and Kazharia and then onwards into China, connecting Hamburg and Hanover to Leipzig and Dresden and Prague. This geographic determinism is what killed the Roman Legions, and – in reverse – led the German Emperor back to Rome a thousand or more years later.

The patterns and flows of the rivers have been used for centuries too, for offence, for defence, for commerce. River traffic has a flow all its own; each river has over the centuries developed its own unique craft, suited to the nature of the river. In the flat lowlands on the outer margins of Europe the craft are broad, flat bottomed. In the higher regions of the rivers where the waters run faster, deeper, the craft are shorter, narrower, sturdier and also more flexible; constructed to survive the torrents or navigate the rocky hazards.

In the early 19th century British traders living in the trading cities of Hamburg and Hanover created the first organised sporting races between teams of modified gigs at about the same time as they began the first yacht clubs and competitive sailing races. Slowly, over the next twenty years or so, the sport crept town by town up the rivers of northern Germany and Poland to reach the heartlands of Bohemia, Moravia and Slovakia.