So what I really did was stamp hard on the foot pedal that brought down the heavy clamp onto my own finger - this is perhaps even more stupid than via hydraulics but fortunately, stupid as it was, I still have a finger.
I danced around the room until the pain subsided enough for me to scream and a friend fetched ice for me. One person asked if there should not be some kind of mechanism to prevent this happening and I said "there is a mechanism, it is called a brain, sadly I did not have it turned on". haha.
I said "pain is all in the mind, but unfortunately I keep my mind in my finger so it hurts like fuck".