It's held in place by a spring clip that sits in a slot in the shaft and expands out into a slot on the inside of the joint. Hold the shaft and hit the joint with a moderate sized hyde/nylon faced hammer and it will come. If it doesn't, hit it harder!
if youre holding the shaft by hand place the bottom end on a block off wood, it will stop the whole lot sliding through you no doubt greasy hand and avoids damaging the spline, they do need a good wack normally.