Kay Underwood, 20, has cataplexy, which means that almost any sort of strong emotion triggers a dramatic weakening of her muscles.

Exhilaration, anger, fear, surprise, awe and even embarrassment can also cause sufferers to suddenly collapse on the spot.

Victims are often left paralysed for several minutes, although they always retain the ability to hear what is going on around them.

Kay, of Barrow-upon-Soar, Leicestershire, who was diagnosed with the condition five years ago, once collapsed more than 40 times in a single day.

She said: “People find it very odd when it happens, and it isn’t always easy to cope with strangers’ reactions.