Whilst being hover taxiied between hangars, in strong gusty wind conditions, the helicopter rotated rapidly to the right, struck the ground, and rolled onto its side. Both occupants were able to evacuate the machine without injury. The instructor pilot reported that the helicopter was being flown by the student pilot at the time. With the wind gusting from the south, the aircraft was lifted into the hover on an easterly heading, then rotated to the right through 180 degrees. As it approached a westerly heading it swung rapidly to the right. Full left pedal and power reduction failed to arrest the rotation which continued for two or three turns before the helicopter struck the ground and rolled onto its side. No mechanical defects were reported that may have contributed to the accident. It was the opinion of both the instructor pilot, and the operator's chief pilot, that the accident was consistent with the loss of tail rotor authority.