After landing, the pilot was taxying the aircraft along a marked taxyway between two hangars. Several aircraft were parked in the vicinity, and the pilot taxied at a slightly higher level than normal in order to reduce the effects of downwash. He suddenly noted cables just above eye level, and banked steeply to the left in an effort to avoid a collision. However, the main rotor blades struck and severed the cables, which were a pair of disused Telecom lines strung between the hangars, and both blades then struck the ground. The cables were not marked, and at the point where they crossed the taxyway they were 6.6 metres above the ground.