It won't hurt a bit. Promise

Mind and Body: The ultimate NY club sandwich, served with Kung Fu relis h by Shaolin Grandmaster Alan Lee. Photographs by David Gamble

Tomorrow, several hundred New Yorkers will cram into a small, but very Zen, eighth-floor space on 28 West 27th Street for the annual public demonstration by the Chinese Kung Fu Wu Su Association. What they will get, for their $10, is a rare glimpse into an extraordinary world of physical and mental prowess. The Association's piece de resistance is shown right, a 6ft-high club sandwich composed of beds of nails, human beings and a topping of solid concrete which, in a final, dramatic flourish, is smashed in two with a sledgehammer.

The nails are six inches long and very sharp. The man at the bottom of this particular pile is Robert Thomas, by day a successful Wall Street banker. Incredibly, when this demonstration was over, there wasn't a mark on him. Crucial to success and safety is that the human sandwich remains completely upright - if it begins to topple, those stood around will rush in and hold it up. Grandmaster and Taoist priest Alan Lee (top) is the presiding genius behind these displays. He began training at the age of seven, in China, under the tutelage of his father, a Master of "Southern Stone Fist" Shaolin Kung Fu. When Lee emigrated to America he became an engineer, but continued to pursue his fist love, martial arts, setting up the Association in 1967. Now retired, he devotes himself more fully to his students, who range in age from seven to 70, and come from all walks of life.

The style of Kung Fu taught by Lee dates back more than 6,000 years and focuses on the development of chi (the vital energy which circulates around the body) in the service of both self-defence and healing. Selection for training, which involves years of mediation and exercise, is very strict, because the skills taught are so potent. All Association trainees are fingerprinted by the FBI: if they can break a concrete block in their hands, the reasoning goes, imagine what they could do to another human being. For some this martial art is already helping them make a killing - on Wall Street that is. Jonathan Dyson