Nothing would touch it.

A mate used a large blow torch (not a little plumbers one) and heated it to buggery until the whole stub was roasting.
We were hitting it with various cold chisels from behind, having removed the backplate.
Absolutely nothing. All we did was turn it blue and put a tiny nick in it. The chisel was hard and sharp, sparks were coming off it but nothing doing.

I ended up removing the stub axle and sending it up to another mates house where he ground one side of the bearing flat and tapped it off.

Funny as I didnt see any mention of beating 7 shades out of a bearing in my Haynes BOL. I must have missed that step...