-Philip- Here are a couple of photos of my father, Donald Sevier Ham on his trials machines. The girder fork machine above is an ES2 that he was riding in the Land's End Trial in 1948 and about to tackle the Beggar's Roost hill; look where his eyes are focused to see how steep the hill was! This was 100% concentration.
The second photo shows the ES2 just starting the climb at Blue Hills Mines, near St Agnes in Cornwall; again on the Land's End Trial.
The last picture shows his 500T getting the better of him and he referred to it as "Waltzing Matilda".