Instrument Panel Ground

A question has arisen about the way in which ground (earth) is provided to the instrument panel.  Its only need is to provide a ground return for the panel lights.  All other ground returns on the instrument panel are hard wired to ground using black wires.  The wiring diagram, as shown in the Workshop Manual, uses the universal ground symbol in a few locations, such as the Horn Push and the Direction Indicator Warning Lamp.  This is misleading, the Horn Push is hard wired to a black wire from the wiring harness.  From what I have seen on, what I believe to be original wiring, is that the physical ground for the instrument panel is provided via one of the ground lugs in the wiring harness that is connected to one of the small bolts that connects the panel to the wooden dash.  The ground lug is secured between a large flat washer and the lock washer of the bolt.  Here is a view of the back of the instrument panel as it was removed from Lazarus, my 52TD:

Look at the lower right end of the panel and you can see the ground lug on the washer.

Here's an expanded view:

Here's a view of the back of the inspection socket:

The red insulator is present and the terminal is not grounded.

It has been suggested that the Inspection Socket terminal can be used to provide the physical grounding by leaving off the inside insulating sleeve and replacing it with a ground lug.  IMHO, that is not the way to go and was not done by Abingdon. 

The 53TD that I'm working on has been modified as some suggest.  However, the wiring and the yellow insulator, are obviously not original. :

FYI, the ground lug matching the one from Lazarus is present on what's left of the harness:

Not hard grounding the Inspection Socket may save you much grief if there's ever a question of +/- ground. Red is used to indicate a positive voltage, black for a negative voltage.