The aircraft was observed approaching to land on Runway 21. It bounced on landing and then rocked from one mainwheel to the other before veering off the left side of the strip and running through a fence. The pilot reported that the wind was straight down the strip and that on touchdown the aircraft swung left suddenly. He was unable to control the swing. A witness on the ground reported that the wind at the time was from the south-east at 15-20 knots but favouring Runway 21. He saw the aircraft bounce a few feet before touching down again on one mainwheel and then the other and then veer off the strip. No fault was found with the wheel brakes which might have caused the swing. This accident was not the subject of an on-site investigation.