The pilot advised that during the landing roll on bitumen runway 36, the aircraft swung sharply to the right. He applied left brake to correct the swing. The aircraft began to straighten but then it veered sharply to the right again like a ground loop. The left landing gear leg collapsed and the left wing struck and propeller struck the ground. At the time, the wind was gusting 10 to 15 knots from 010 degrees. After the accident, the pilot thought that the left brake might have failed causing him to lose directional control. An engineer inspected the brakes and advised that there was no evidence of a brake failure. However, the engineer rebuilding the aircraft discovered a pre-existing fatigue crack through about half the left landing gear leg. It is probable the fatigued landing gear leg failed during the landing roll. According to the engineer, the landing gear legs in VH-ICA were of the thicker metal version. Therefore they were not subject to mandatory magnetic particle method crack testing as were the earlier version of spring legs in accordance with Airworthiness Directive AD/Cessna 188/3. Significant Factors This accident was not the subject of an on scene investigation and there was insufficient evidence available from other sources to determine the factors that led to the accident. Safety Action The maintenance organisation rebuilding VH-ICA advised that a defect report would be submitted to the Civil Aviation Authority concerning the pre-existing crack found in the landing gear leg. The Bureau of Air Safety Investigation advised the Civil Aviation Authority of the fatigue crack by way of the Bureau's weekly summary of occurrences.