Load it up with penetrating spray (around the top of the blade + in the little hole and underneath the blade).

Find somewhere strong to rest it so it's sitting on the casing and not on the back end of the gears (I used an old pallet), clamp it down with C Clamps (the Irwin quickclamps can't handle it and will come off) and give it a good whack or two.

If you're lucky it'll go through and everything's all good. The first one I did I had to get out an SDS Drill on chisel mode (so it goes up and down and not spinning!) and give it a solid blast until it came out.