Technical Removing the tire from a Topolino rim

[Boobtube]

Can anyone provide advice on how to remove the tire from a Topolino 500A? These are not like modern rims. They have very high outer ridges and I can't seem to get the tire irons to lift the tire over them. I'm afraid of bending the rims in the attempt. Has anyone done this job? I just need to get one side off to replace the inner tube.

 

[ZaphodB]

You are ensuring that you've pushed the beads fully off the edge ?
and also ensuring the opposite side of the bead (to where you're trying to lift over the rim edge) is sat in the hollow of the rim?