In the early 1920s the world of ladies' fashion was turned on its head by Gabrielle Chanel. Her career as a couturiere began modestly enough just after the first World War, in Deauville on the northern coast of France. Within a few years, however, her influence as Coco Chanel had freed women for ever from the tyranny of corsets.
Her distinctive styles were elegant and simple, comprising softly tailored suits with straight boyish lines; she introduced "bobbed" hair and costume jewellery, and her No 5 perfume, named after her lucky number, became a world bestseller. Coco Chanel, in fact, became synonymous with "chic".
But she also started an even more enduring trend. Cruising on the Mediterranean in the Duke of Westminster's yacht, Coco inadvertently developed a suntan. Her influence was such that, almost overnight, bronzage became a status symbol.
Its image was inverted from the mark of the humble working man to an icon of the wealthy, leisured and successful classes. Very soon the Victorian ideal of a lady's soft white skin was abandoned with the parasols and bonnets, and several generations of heliophiles nurtured their suntans on the beaches of Spain and Greece, and on the ski slopes of Switzerland and France.
It is only in recent times that the dangers of this fad have been appreciated. They are not a consequence of the heat or the light the sun provides, but of another invisible, impalpable ingredient, the short-wave energy of ultraviolet radiation.
UV is similar to visible light waves or radio waves but, unlike these two, ultraviolet radiation is harmful to human health and to our general environment, and it streams towards us from the sun continuously. The ozone layer, some 15 miles or so above our heads, gives some protection, but it only shields us from the very worst effects.
The dangers of exposure to UV are threefold. First, it affects the skin, at the very least by causing accelerated ageing or wrinkling, or much more seriously by causing mutations which may lead to various forms of cancer.
Second, excessive exposure to UV can cause the lenses of the eye to cloud up with cataracts, a condition which may lead to blindness if untreated. Excessive exposure to ultraviolet radiation may also affect the body's immune system, and thus its general ability to resist disease. And, of course, it is UV that causes that painful reddening, blistering and peeling of the skin known to the medical profession as erythema, and to you and me as sunburn.