Self-awareness in dreams is more common than we think. So why do those who inhabit a shimmering nocturnal world keep quiet about it?

THE Marquis d'Hervey de Saint-Denys was a dream machine. He dreamt about the things he most wanted - including passion. In the 1860s, he went to great lengths to ensure two women appeared in his dreams. At dances in waking life, he waltzed with each when a specific tune was played. A musical box then played the tunes while he slept - evoking them in his dreams.

Lucky man. Most of us never have so-called "lucid dreams" - dreams in which the sleeper becomes aware that he or she is dreaming. This self-awareness changes the nature of the dream, giving a strikingly convincing imitation of waking life, often positive to the point of elation. It can mean an exotic trip, a promotion, a celebration - anything you want.

Sounds magical? Well, yes. So why do we not know more about the shimmering world of dreams which grips our imagination as surely as the weather and the royals? Those who experience them regularly tend to keep quiet about their nocturnal adventures for fear of...