Well done for finding this video and thanks, for posting this link. I have not seen it before and really enjoyed watching it and seeing so many old faces again. I was there, and knew the person that shot and posted the video. Occasionally I can be seen in the background taking photos.
I frequently ride past the spot where all the Wendover Bashes took place which always brings back great memories of the four 'bashes' I went to.
Geoff Apps was a motorbike trials rider and so had designed the course that would challenge motorbikes. It may look as the riders aren't very skillful, but I can tell you that the soil there is very loose and wheels have a strong tendency to slip down the camber making some of the sections almost impossible to ride.