Hi, I'm trying to access the controller on an Electrobike. It's fitted in the crankcase

[Montmorency]

Hi, I'm trying to access the controller on an Electrobike. It's fitted in the crankcase and I can remove the left crank and unscrew the lock ring behind it but the right side has a grey metal disc on the chainwheel the prevents me getting at whatever is behind it. Does anyone know how to remove that disc? There is a picture of the disc on Sailorbrian's post.