The Romans washed with lavender — their word for it, lavare, means 'to wash', and it is where our name for the plant comes from.

Roman legionaries carried little cloth bags of dried lavender to freshen their beds, and Roman doctors prescribed it as one of the earliest sleep remedies.

Modern medical trials at the University of Southampton and at Wesleyan University in Connecticut, in the 2000s, tested it: people who slept in a room lightly scented with real lavender oil reported deeper sleep and woke feeling more rested.

Lavender grows in the hot dry hills of Provence in France, where the fields turn deep purple every July; you can still buy the little muslin sachets that Roman soldiers would have recognised.

Try this: dry a handful of lavender flowers in the sun for a week, tie them in a scrap of cloth, and put the bundle inside your pillow.