As if we did not have enough to cause us sleepless nights, the Royal Society for Public Health has demanded a ‘national sleep strategy’, presumably overseen by some sort of Czzzzar, to lay down, and one very much hopes rigorously enforce, strict guidelines on how long each of us should sleep. The ancients knew all about it.

The Greek doctor Hippocrates commented that while it was natural to be awake during the day and asleep at night, pain, distress, psychological problems, symptoms of some physical ailment, especially indigestion, or simply old age were the likely cause of insomnia.

For Galen, sleep and insomnia originated in the brain. The more active the brain during the day, the better the chance of a good night’s rest: the brain needed sleep to recover. Ancient dream theory suggested that during the night the brain was trying to deal with the ‘residue’ of the day. The atomist poet Lucretius (1st century bc) not only argued that what gripped our waking hours also dominated our own and animals’ dreams (those twitching hunting dogs), but also described anxiety dreams (falling off cliffs) and wish-fulfilment dreams (causing nocturnal emissions), all likely to wake us up.

Inevitably, the philosopher Seneca had the answer, provided by his friend Sextius. It took the form of a nightly confessional, in which he pleaded his cause before his own tribunal (once his wife had learned of his habit and respected his silence with her own). Surveying the whole of his day, retracing all his words and deeds, he tells us he concealed nothing from himself and omitted nothing, as he subjected his soul to a rigorous cross-examination: ‘What bad habit have I cured today? What fault have I resisted? In what respect am I better?’ He delights in the ‘tranquil, deep and untroubled sleep’ that ensues after his soul has duly delivered its report.

One might not have thought that soul-searching was the best way to get to sleep, but then not many of us are multi-millionaire philosophers.