The phrase “robber baron” is popularly used to describe the titans of late 19th-century US business – men such as John D. Rockefeller, Jay Gould and John Pierpont Morgan. But the term is much older. The Rhine valley has been Europe's principal highway for 1,000 years. Today the principal route through it is by road, along two parallel motorways. But for most of that time, traffic floated down the river.

Then as now, the people who lived along the river bank provided services to the users and collected revenues. Then as now, they hoped to minimise the services while maximising the revenues. Between Bingen and Koblenz, the river enters the Rhine Gorge. The narrow passage means that even in the 13th century it was easy to impede the flow of traffic. For centuries, the Holy Roman Empire derived patronage by assigning rights to a limited number of toll points. But when the Emperor Frederick III died in 1250 there was no agreed successor, and hence no regulator. This was when robber barons started to collect unauthorised taxes on the gorge.

There was a vigorous consumer response. The first Rhine League was an association of merchants given legitimacy by aristocratic participation. The League's simple, brutal and effective strategy was to employ a militia to raid the toll gatherers' hideouts. After attacking the notorious Werner von Bolander, they stormed and destroyed the redoubt of the resourceful Philip von Hohenfels, who built a replacement castle on a rocky outcrop. His Castle Reichenstein, reconstructed at the start of the 20th century, is today a luxury hotel.