The poison is tetrodotoxin, found in the liver and ovaries of a certain type of blowfish, called fugu, whose flesh is prized as a delicacy in Japan.
The fugu (fugu rubripes of the Tetraodontidae family) contains enough poison to kill an entire restaurant if it is not prepared carefully, and the government, understandably, has strict regulations concerning the serving of fugu to the public.
Restaurants which want to offer fugu must get special permission and only chefs who have taken special training may prepare the fish. The training shows how to cut open and clean the fish without puncturing the poisonous organs which could make the entire fish dangerous to eat.
Fugu is extremely expensive - a meal of fugu at a good restaurant could easily cost over pounds 100 a head. But the fish has very little taste. It is usually served partly raw, with the thin, white slices of flesh arranged on a plate to look like a chrysanthemum blossom, and the remainder put into a stew with vegetables. Some devotees say the fish has a special texture, but its popularity is no doubt partly due to the lethal aura surrounding the ugly creature.
For real aficionados what makes fugu so compelling is precisely what makes it so dangerous: the poison. Ingested in small amounts, it produces a pleasant numbness, probably something like cocaine. Ingested in larger amounts, it produces death.
Every year Japanese people die from fugu poisoning. According to the Ministry of Health and Welfare, the worst year since records began after the war was 1958, when 176 deaths occurred. Most of these deaths happen in private homes, when people without expert knowledge of the fish prepare and cook it. More recently the figures have gone down, and now an average of four or five people die each year.
The most famous case of fugu poisoning occurred in 1975, when Goro Mitsu, a renowned actor of the kabuki theatre went with friends for a meal in Kyoto. The restaurant, called Masai, served fugu, and at Mitsu's request, some of the poisonous organs were presented on a plate.
What happened that night has never been explained fully, but apparently Mitsu, a well-known fugu gourmet, dared his companions to eat some of the poison, but all refused. So he seems to have eaten more than his share. He went back to his hotel and told his wife he felt like he was flying. He became so numb he could no longer stand and his last words to his wife were that he was happy she had not come to the restaurant or the same would have happened to her. He died in the early hours of the morning.
Mr Obuchi, the Tokyo restaurateur with whom I raised the subject, said he had never tried eating the poison of the fugu and would not serve it to his customers. He has a fugu licence for his restaurant, but said that if the authorities found out that he was 'playing' with the poison, he would almost certainly be shut down. He said that in the more rebellious west of Japan there were restaurants that would serve the poison to special patrons known to the owners. The judgement of these chefs is said to be reliable in the matter of how much poison to give to an individual, but if this column ceases to appear in the near future . . .