Easy coming off, pain is putting it on.

There should be a circular metal clasp holding the knob onto the metal rod. I just used a flat head screw driver to pry it off.
However, I had to get my mate to put my knew one on as the cirlus clip needs a tool to put it a new one back one.
Bt..once you take the clip off, you can't reuse it (i think).
Someone else may be better to advise of a easier way to rmeove it.