No Stu, the black box at the top is the voltage regulator. It's a V Reg 2 from A O Services which I fitted after the previous CMES unit which went AWOL.
The little switch at the left side is a simple on/off switch. You've reminded me I don't really know why I fitted it considering that it's wired to the main supply and not the ignition and the fuses protect the wiring in case of a short, so it's redundant. What I should do is rewire that switch to earth the magneto to act as an on/off switch to give a modicum of security. Will do.
Thanks for jogging me into action, now where did I put the wiring connector crimper?
Alan