replacing a choke cable?

ok, i have re-routed one of my useless heater cables to become a choke cable. up the front i have bought a cool old choke pull (from an Austin or Hillman i think), but when i got it home i noticed that there was no obvious way to remove the cable from the knob so that i could fit the knob to my own cable. i presume there must be some way to remove it, otherwise you would have to replace the knob everytime a cable broke, so was just wondering if there are any known ways that these cables are attached into the knobs? or do i just have to join the cables under the car?