MkIII wiring, ignition light

[rsk289]

I've finally reached the point today when I connected up the battery and have checked all the electrical circuits. All satisfyingly perfect, except...
The ignition warning light is not coming on. The situation at present: the engine is not running and not complete (carb, exhaust etc.). I have an Autolite alternator and an Autolite external regulator, all wired as per the MkIII or 427 Lucas SF4 wiring diagram. I have earthed the alternator and the regulator (control box). The only connection on the whole car that is not there is the feed to the coil from the ignition switch, and the lead from coil to distributor (coil and distributor not yet fitted). Everything else is connected.
I've checked the wiring as per diagram for continuity and it all conforms. Obviously I cannot start the engine, but I would expect the red warning light to come on when I turn on the ignition. It doesn't.
I am the first to admit that I don't understand how these things work. It seems odd that there is no connection to the 'I' terminal on the regulator, but that's what the diagram shows.
Can anyone help with this? Should I wait until I can start up for the cam break-in, and hope the light comes on as it should?
I'm wondering if I would do better to bypass the ammeter permanently and just use the 'I' connection for the warning light - but I'd prefer to have it working as it should.

Roger