The impor­tance of Beck’s rectilinear, topologic 1933 diagram is widely recognised and praised by graphic designers. Many wonder why Beck never extended his ideas outside London. The answer is, he did – to the nearest major subway network to London: Paris.

Mindful of Paris’s prominent position as the most visited city on the planet, the forward-thinking head of ratp’s design department, Yo Kaminagai, ordered his map designers to begin a quiet cartographic revolution from 1987 which finally resulted in the commis­sioning of a diagram.