You may have to heat the stub axle around the ball joint stud to break the seal. Don't overheat the stub axle by making it red hot. You'll probably set the ball joint rubber boot and grease alight so do this outside where you can't set the garage ablaze
You may be lucky that once the stub is heated enough the joint will pop under the pressure of the suspension spring.
Either install a spring compressor to prevent the whole shebang from potentially flying apart or wear your cricket pads, box and a pair of steel cap boots.
Almost forgot, don't go smacking the stub axle with a hammer (if required) until it has cooled down and don't quench it with water to cool it faster.
Edited by S pack, 07 February 2016 - 08:45 PM.