On the slightly OT, err, T of removing cranks, I have a fantastic tool - a Crank Extractor!
So do I! I also have a spanner, and 14stone of body weight.... that b***er wasn't shifting, it started to strip the threads on the crank! I even rode around for 2 weeks with the nut missing. It didn't budge a nanometer.
Heating the crank with a gas flame, didn't help either. Neither did soaking in ammonia.
Eventually (thanks to Mussels) I removed it by using a Dremel and a hack saw to cut a slot in the crank. A swift bang on a screwdriver inserted in the slot and the crank fell off.
On examining it closely the actual amount of "weld" was practically invisible, but it was able to hold the crank on despite all that force & other "encouragement".
Aluminium + Steel + Water = Electrolytic Chemical Weld.....it's a well known problem encountered anywhere where alloy & steel meet. In particular cranks + BBs, pedals+cranks and seat post + frame. Grease the parts before assembly if you ever want to separate them in the future.