The driver – a round, balding man in a well-worn cap and stained overalls – had been briefed at length about this deadly chemical by his supervisor and some idiot from the Serbian Safety and Well-being Transportation Oversight Ministry. Some years ago this substance had killed eight thousand people in Bhopal, India, within a few days of a leak from a manufacturing plant there.

He’d acknowledged the danger his cargo presented but, a veteran railwayman and union member, he’d asked, ‘What does that mean for the journey to Budapest… specifically?’

The boss and the bureaucrat had regarded each other with the eyes of officialdom and, after a pause, settled for ‘Just be very careful.’

The lights of Novi Sad, Serbia’s second-largest city, began to coalesce in the distance, and ahead in the encroaching evening the Danube appeared as a pale stripe. In history and in music the river was celebrated. In reality it was brown, undramatic and home to barges and tankers, not candle-lit vessels filled with lovers and Viennese orchestras – or not here, at least. Still, it wasthe Danube, an icon of Balkan pride, and the railwayman’s chest always swelled as he took his train over the bridge.

His river…

He peered through the speckled windscreen and inspected the track before him in the headlight of the General Electric diesel. Nothing to be concerned about.

There were eight notch positions on the throttle, number one being the lowest. He was presently at five and he eased back to three to slow the train as it entered a series of turns. The 4,000-horsepower engine grew softer as it cut back the voltage to the traction motors.

As the cars entered the straight section to the bridge the driver shifted up to notch five again and then six.