Modern lifestyles may no longer be constrained by sunrise and sunset, but light remains one of the most powerful influences on our behaviour and wellbeing. This realisation has fuelled a “sleep hygiene” movement, whose proponents point out that bright lights before bedtime and spending the whole day in a dimly lit office can dampen the natural circadian cycle, leaving people in a continual mental twilight – dozy in the morning, and too alert to fall asleep promptly at night.

Rosbash welcomes this new awareness. “It’s been overlooked for a long time as a real public health problem,” he said. “All of western society is a little bit sleep deprived and, when I say a little bit, I mean chronically.”