Pull the base of the gaitor towards you, Then roll it upwards up to the top of the gearknob, Juo wil then see a little round silver clip that crimps to the gear stick shaft & holds the Knob in pace, I managed to cut mine off using a pair of side cutters but you can prise it open with a flat screwdriver, Once that is off wiht a bit of force the Knob should just lift up,
When you are fitting your new one you will need a jubille clip to replace the original silver clip.