You wake with a start. The world around you is pitch black. Your partner is sleeping, provocatively peacefully. You reach for the alarm clock, then curse it. It’s 3am. Again. Why does this keep happening? Is it symptomatic of stress, or a sign of something more sinister? Or perhaps we’re worrying needlessly, manufacturing a “health crisis”?

“This was the whole reason I wrote my book,” says Russell Foster, professor of circadian neuroscience at Oxford University and author of Life Time: The New Science of the Body Clock. “I wanted to say: here’s the science. Now stop worrying about it.”

The Telegraph London