Always serve your hippo stewed in vinegar

Feeling peckish? If you happen to be tucking into a moose, it's worth bearing in mind that, according to the Inuit, "the finest tidbit of all" is the nose. Contrariwise, if witchetty grubs are on the menu, "the one thing to remember is not to eat the head".

Don't be tempted to scoff too many false morels (Gyromitra esculenta); they contain a toxic element that happens to be the same chemical used as rocket fuel in the American space programme. However, cordyceps, a fungus that grows as a "live parasite on insects or worms" is eaten with relish by the Chinese and Tibetans. This aphrodisiac is "customarily consumed in a rich chicken broth in the late evening". Should hippo be on the menu, remember that it "tends to be greasy and needs the addition of wine or vinegar". No such worries with puma, which, according to no less an authority than Charles Darwin, is "very white and remarkably like veal in taste".

Along with "washing-up", "sonofabitch stew," "sin-eating" and "geophagy" (the consumption of earth), these delicacies are among the 1,260 entries in Alan Davidson's magnificent Oxford Companion to Food (OUP, pounds 40). It is a major and serious work, but engagingly eccentric round the edges. Aside from the effort involved in lifting this massive tome, the main problem in using it is that one thing leads to another. Look up "USA", for example, and you find a paean to roadside diners ("Americans have a gift for seeing opportunities where others might see only problems") that leads to "hamburger" and thence to a two-page entry on "beef", where this reader found himself seduced by a cross-reference to "rissoles". This proto-burger turns out to have had a long and varied history: "Around the basic formula, there exists a penumbra of variations that permit making fish rissoles and vegetarian rissoles (even a fruit rissole in the 14th century)."

Such felicity of expression and love of the recondite detail is typical of Davidson, who wrote 80 per cent of the 1,020,000 words in this cornucopia. "From the start, I intended it to encourage browsing," he said. "It's meant to be a lot of knowledge and plenty of entertainment." A major strand of the book is the 130 entries devoted to national cuisines. Virtually every political entity in the world is covered. Another recurring theme is food writers. Davidson is particularly keen on an overlooked pioneer called Karl Rumohr (1785-1843). He approvingly quotes Rumohr's denunciation of snacking: "A `nibbler' can be recognised immediately by his decaying teeth, swollen eyes and dreamy appearance."

Originally planned to be completed in seven years, Davidson's magnum opus ended up taking 20 years. "Yes, it was a rather long period," he mused in his grotto-like study at World's End, Chelsea. (In order to accommodate his 5,000 reference books, the Companion was in fact written in a separate flat a few doors away.) "The quality of my enthusiasm changed as the job went on. At first, there was the enthusiasm of the pioneer. Towards the end, my enthusiasm was more along the lines of "Let's get this thing done." My wife had been taking this point of view for 15 years." A diminutive 75-year-old, hunched from decades of poring over food books, Davidson is nevertheless full of beans.

Perhaps uniquely for a reference book of its scope and authority, the Companion to Food is gemmed with jokes. Sometimes, as with "washing-up," these can extend for a whole entry. "I suggest that washing-up should be seen as the climax of a meal," the author explained to me. "This starts with hunting and gathering at the supermarket, followed by cooking and eating the food, and culminates in purification of the dishes, which in some cases may be entrusted to the senior male member of the household."

Like the spurt from chicken a la Kiev (lukewarmly described as "a Soviet hotel and restaurant classic"), quirky details leap from the pages. Davidson always finds room for a piquant quote, as in the entry on "head", which contains an extended description of eating the Afrikaans speciality of baked ox-head: "One's first emotion, on seeing this immense and horrific roast - in which the baked eyes stare with an expression that is ludicrous as well as baleful - is one of profound shock. Two of my fellow gourmets were so overcome that they had to leave the table."

Davidson sketched out the path that led him from the diplomatic service to the production of the greatest food book in the English language. "I think that I had just a normal interest in food until we were posted to Tunis 36 years ago and there my wife made the fateful request to get her a book about Mediterranean fish which she found very confusing. There were wonderful fish in the market, but with so many names in Arabic, French, Italian, Maltese, they were impossible to sort out. It turned out that there wasn't such a book, so I decided to put together a booklet. And that might have been that, but for the fact that one of my colleagues passed a copy on to Elizabeth David, who was having trouble with the fish names in her Italian book at the time."

The doyenne of English food writers passed the pamphlet on to her editor at Penguin, and Davidson was asked to expand it into a Mediterranean seafood book. Did he get on with Elizabeth David?

"Yes, well, I like to think so. I always felt she liked my wife particularly, and she was very tolerant of me. She'd say, `Alan is doing some useful things but sometimes he gets a bit mixed up and he doesn't know as much as he might about English history.' She contributed quite a bit to Petits Propos Culinaires, a quarterly food magazine I produce, so for that limited purpose I was her editor. I discovered what an extraordinarily sharp memory she had and how she insisted on getting every detail right. It was salutary."

Davidson's voice carries more than a trace of his Yorkshire background. His slightly camp delivery, peppered with donnish humour, is somewhat reminiscent of Alan Bennett. This emerged most strongly when he embarked on a eulogy about desserts. "I'm very partial to traditional English puddings, like suet puddings and steamed puddings of various sorts. With custard. And when I say `custard', I don't mean some fancy French custard that you whip up yourself. I mean Bird's custard. Bird was a great man. He invented his custard for his sick wife. Good old Bird."

Davidson's determinedly non-didactic approach to food emerges in the entry on "corned beef", which extols "the classic English salad" consisting of "slices of corned beef, tomato quarters, slices of beetroot and salad cream (NB, not mayonnaise). This is delicious." Spam is another unfashionable favourite. His entry notes its popularity in Hawaii, and that Spam musubi, Spam sushi and Spam wonton "are all delicious, as is Spam tempura, akin to the British invention of sliced Spam fried in batter."

Though the very production of such a book is a rebuff to the universal prejudice that the English are indifferent to food, Davidson's entry on England makes the point that "until the very recent past", our food has been "lacking in variety, finesse, imagination and innovation." These traditions are "surprisingly persistent and resilient." The recent fashion for TV chefs and dining out "constitutes, so to speak, a surface froth above what have been deep and almost still waters".

Having laid this banquet before the public, Davidson has embarked on a new project: a series of essays about the great screwball comedy heroines of the Thirties - Claudette Colbert, Myrna Loy, Ginger Rogers.

Not that Davidson is deserting food entirely. He has plans for "two teensy books" on bread-and-butter pudding and trifle. "It is absolutely fundamental to English food. Trifle is something people feel strongly about. When we had a recipe for trifle with jelly in Petits Propos Culinaires, two subscribers cancelled their subscriptions at the thought of including jelly. Who would have thought that trifle could cause such upset?"