Thanks for the reply. The last picture was so poor it didn't really show the inside of the spindle but it looks like this, which made me think another tool may be necessary:
Nah, it's just a double hex like the rotor bolt on Shimano freehubs. On the hubs it's necessary to provide clearance for the axle, on the cranks there's no real need for it.
Thanks for the reply. The last picture was so poor it didn't really show the inside of the spindle but it looks like this, which made me think another tool may be necessary: