The pilot had previously discussed the strip with the station owner but had not ascertained its length. On overflying, the pilot assessed its length as 600 metres, and after checking the P chart he calculated that 500 metres was needed for a landing. The pilot stated that he crossed the threshold at 65-70 knots with full flap selected. Ground marks indicated that the aircraft touched down 195 metres past the threshold. It then bounced twice before overrunning the strip, striking an earth mound and running through a depression. The grass strip was measured as 408 metres long and was slippery from rain which had fallen the previous day.