Dr Allen, 35, a scientist, suffers from bouts of "cataplexy", a rare symptom of narcolepsy, triggered by strong emotions-such as fear, surprise or laughter.

The attacks cause her to lose control of her body and she collapses into a deep sleep - although she remains conscious throughout. ?

Each collapse lasts between 30 seconds to five minutes and at its worst Claire can endure up to 100 attacks each day. ?

Claire, from Cambridge, described how she first loses her speech and vision before her body buckles - but she remains completely "awake". ?

She said: "The attacks are caused by any emotional surprise or shock but laughter is definitely the strongest trigger.

But the new drug Xyrem puts Claire into a deep sleep for three-and-a-half hours so she must take a second dose in the middle of the the night to get a full seven hours sleep.

She said: "For the last five years I hadn't slept for more than an hour at a time so the first time I slept for more than three hours it was incredible. ?

Researchers have found that narcolepsy may be caused by an irregularity to the brain cells which control the sleep hormone hypocretin. ? An estimated 25,000 people in the UK suffer from narcolepsy but many remain undiagnosed due to the varying nature of the symptoms.