Series 3 ELECTRICAL ISSUES

I have recently acquired a Series 3 109 ex MOD FFR 1980/ The electrics are a bit shaky but I'm pretty sure the main feed to the ignition switch (and thence virtually everywhere else if I've read the diagram correctly) has gone from intermittent to broken. A direct feed from the battery has corrected most of this. My question is where does the red/white feed to the ignition switch come from I don't think its the coil and I can't see which fuse it might be. Any offers ???

According to the official workshop manual for the standard SIII it goes from the ignition switch to the starter solenoid.

I have a loose spade on the fusebox. Switches everything off now and then. I have learnt where to belt it to get things back on again.