While flying straight and level at 45 knots, the engine began to splutter. The pilot immediately used the hand fuel pump but his efforts were unsuccessful and the engine stopped as a result of fuel starvation. From the air the ground below looked suitable for a forced landing. However, at a low height it became apparent that the ground surface was rocky. During the landing roll the left mainwheel struck a rock. A subsequent examination of the fuel system discovered a piece of red, electrical, insulation tape within the fuel tank. This tape had blocked off the outlet pipe from the fuel tank to the engine. The pilot believes that the piece of electrical tape had probably originated from refuelling equipment and entered the tank during a refuel from drum stock.