Yesterday the trust, a charity which carries out research on the conservation of gamebirds, mammals and fish, proudly showed off the hare population explosion it has engineered at a Leicestershire country estate.
In 1991 there were only six animals on the 316-hectare farm. Now there are more than 100 and a dozen could be seen sprinting across fields yesterday in the spring sunshine. They can reach 30mph and weigh three times as much as a rabbit.
At the Loddington estate, near Rutland, the farm has been managed in a "hare friendly" fashion over the past four years. Foxes have been shot in early summer, when they eat the young hares - leverets. The landscape and crop growing have also been changed to benefit the hares, whose decline has been linked with the spreading of intensive agriculture. Where once only five different crops were grown at Loddington, now there are eight.
Land taken out of production to gain Common Agricultural Policy set-aside grants has been deployed in ways which benefit hares and game birds. Strips of it run across or alongside the largest fields, planted with brassicas and cereals to provide food and cover.
The trust has also been monitoring hare numbers on a nearby farm of similar size. There, where foxes have not been controlled and cropping patterns and field layouts left unchanged, the hare population has remained in single figures.
Dr Stephen Tapper, the Game Conservancy Trust's head of research, believes a recent report on the hare population from Bristol University researchers was too pessimistic. He puts the total number of brown hares in Britain at one to two million while the Bristol researchers' estimate was 600,000 to 900,000. He accepts that numbers dwindled rapidly during the post-war intensification of agriculture but believes the arrival of set aside may be starting a recovery.
There are many potential causes for the decline - disease, predation, hunting, pesticides and silage cutting which chops up leverets. The trust blames the rise in fox numbers and a lack of summer food due to modern farming techniques, which have cut crop diversity and eliminated spring sown cereals.