Since the trust is a charity dedicated to scientific research, it is debarred by law from making political statements. Nevertheless, its new book amounts to a manifesto - a statement of its position in various fields, many of them controversial, reached after six decades of investigation. Its text, written by 16 scientists and edited by Dr Stephen Tapper, is often disappointingly cautious - doubtless for political reasons. Yet it contains a great deal of fascinating information, and amounts to a valuable snapshot of British game and its predators at the end of the millennium.
The trust is now a formidable organisation, supported by 27,000 members (mostly landowners and shooting men) and employing almost 70 scientists, with an annual budget of pounds 4m, but no regular support from the Government. Last year alone its specialists published 49 scientific papers. As its latest annual report remarked: "It has no equivalent anywhere in the world."
Its hallmarks have always been practicality and common sense, and the central theme of A Question of Balance is that man has not only a right but also a duty to manage his environment in a positive fashion.
Game, the trust says, should be regarded as a crop like any other: just as a farmer grows wheat or barley, so his land - if sympathetically managed - will also produce game, which can be harvested from year to year, producing extra income.
The trust's own research has shown that two elements are essential to game production: one is good farming, the other control of predators. Much of the trust's early work focused on the grey partridge, which has been in serious decline for the past 40 years. Research revealed that in the first weeks of life, grey partridge chicks depend almost exclusively on insects to obtain the protein which they need for rapid growth. In the early 1950s the introduction of chemical herbicides eliminated many of the weeds on which insects live, and so removed about three quarters of the partridges' potential food supply.
To give the birds a better chance, the trust developed the concept of "conservation headlands" - strips round the edges of arable fields which are left unsprayed, or selectively sprayed, so that harmless weeds and insects can flourish. It also urged farmers to leave more nesting cover in the form of wider hedges with grass verges alongside, rather than try to cultivate every square yard of their fields.
At the same time, it advocated the culling of predators, principally foxes, stoats, rats, crows and magpies - especially in spring when game birds are breeding.
These pioneering policies have now been widely adopted but nowhere are the results of them more striking than on the trust's own experimental farm at Loddington, in Leicestershire. Since the trust acquired the property in 1992 there have been spectacular increases in the numbers not only of wild pheasants and hares but also of songbirds such as thrushes, blackbirds, dunnocks and chaffinches.
Agricultural output, far from suffering, has also increased and the land itself has been given a far more attractive aspect by the creation of smaller fields and the introduction of varied crops.
The message is the same for many different types of terrain: management for game enhances the countryside. In the lowlands, shooting men plant woods, spinneys and hedges for sporting purposes; on upland moors, they spend fortunes maintaining the heather and preventing encroachment by bracken or coarse grass so that grouse can flourish. Whatever the setting, their efforts benefit other wildlife besides game.
Unlike many conservation bodies, the trust is uncompromising on the need to cull predators. It maintains that there is no sense in letting one species flourish at the expense of several others: everywhere, it says, the aim should be to create and maintain a sustainable equilibrium.
The even-handed nature of the book is particularly evident in the section on foxes. This estimates the spring population at 240,000 adults, and the annual production of cubs at 425,000. If the population remains stable, as apparently it is at the moment, it follows that 425,000 foxes must therefore die every year. Gamekeepers probably kill 70,000-80,000, and fox hunts a further 16,000.
The inevitable conclusion is that by far the greatest killers of foxes are road vehicles - but the book does not condemn drivers or call for lower speed limits. Nor does it point out that, for all the fuss made about traditional hunts, they play a relatively insignificant part in keeping the population down. It merely gives numbers and facts, and states that "statutory conservation agencies" must recognise the need for continuing control, at least at present levels, because: "There could be a loss of species diversity if fox numbers are allowed to increase unchecked."
Sometimes the massed scientists are a bit too guarded - as when they discuss the barnacle geese now infesting Hebridean islands.
In the old days, landowners used to get together every year and decide how many birds to shoot. Now, with the geese protected by law, the population has rocketed out of hand: on Islay alone, more than 30,000 geese are destroying the pastures every winter by grazing and plastering the fields with droppings, and various statutory bodies are compensating the farmers to the tune of pounds 400,000 a year.
This, surely, is conservation gone mad - yet the trust makes only the mildest suggestion: that if numbers continue to rise, and the cost of compensation become "unacceptably high", future measures "might include allowing the species to be shot, with appropriate safeguards".
The advantage of such restraint is that it encourages debate - and that, I suspect, is what the book is designed to do. Its mass of fact, figures and references will provide a splendid basis for discussion.
`A Question of Balance': the Game Conservancy Trust, Fordingbridge, Hants SP6 1EF (pounds 25, inc p&p)