I have had the same problem, but have just discovered it. Carefully remove the metal Kenwood sticker on the speed control knob. Underneath the sticker is the bit that you have to remove. On the back of the knob there are two semi circleer holes that have a plastic, slightly raised clip on the curved part of the hole. with a small screwdriver or thin fingers, push the plastic clips towards the middle of the knob, realising the clip, push it upwards and out of the top of the knob where the sticker was. Underneath that, you will see the end of the spindle and the retaining wire spring clip holding the knob onto the spindle. carefully remove the spring clip, and the knob will then be able to be removed. To resemble, just reverse the instructions, and then glue back the metal Kenwood label, back onto the speed dial. Hope the above instructions are clear enough. It's one thing taking it apart, but another trying to explain exactly what I have done. So I hope it helps anyone in future that is having the same problem:-)
Colin., May 2013