take a run up, put hands on ponys bum and jump!!! i can only do it on my 11.2hh pony!!!! it hurts my legs on anything bigger!!! its fun but you need a quiet sane horse/pony!!!
I was taught at PC Games practices that the faster you go the better you can vault! I was taught to run like hell by pony thundering along, jump with both feet in front of the horses movement and his speed should ping you back up into the air so you just swing you legs back with the force and over. It did seem to work back then, although my pony had a terrible habit of grinding to a halt to eat grass..... and we never looked anything like the pro's doing the Prince Philip Cup! Its the same idea when you get off at speed - you have to land with your feet in front of the ponies movement or else you'll land flat on your face.
I can *just* sometimes do it on my 13.2hh old games pony, but Im not very flexible anymore
Pleased to say I could still do it on my shetland though