The boundary between the eastern and western hemispheres has often been a matter of dispute. In 1634 King Louis XIII personally banned all alternatives to the Paris meridian, while the Anglo- Saxon world insisted Greenwich should be the universal reference point for cartography and time zones. In reality this was a struggle for world hegemony between France and England that lasted two centuries, until the Washington conference resolved the disagreement. Even so, for many years the French continued to use a meridian that ran through their own capital.

The journey Van Cleef undertakes, equipped with only the bare necessities and a GPS receiver, reads like an exotic road novel. He has an eye for the preposterous and absurd that his journey along an artificial straight line naturally brings with it, and he encounters reactions he could not have foreseen, from local chiefs, for example, who want to use him to promote their villages. Then there are the inevitable misunderstandings: ‘A car slowed down and the driver asked through the window whether I needed any help, but no, I was kneeling next to my car only so I could record a zero point.’

The Hidden Order is an atmospheric account of a journey through outlying districts and across deserts, interspersed with passages about geography and history. The slightly melancholy story includes moments of perplexity, such as a subdued New Year’s Eve party in Africa: ‘No ardent hugs. No women clinking lemonade glasses. No explosions of dynamite.’ In the Ghanaian coastal town of Tema the journey ends at the Meridian Hotel, once luxury tourist accommodation, now inhabited by homeless families and criminals. Following that single unbroken line, Van Cleef creates a marvellous portrayal of the differences and the common ground between people in Europe and Africa.

• A thrilling travel story as well as a history of the prime meridian, time zones and the international dateline