John KD4IDY wrote:

I don't recall whether you ever mentioned what the length is of your
coil. Is it an appreciable fraction of the overall antenna height?

Hi John.  The length of the loading coil is 800 mm.  Because it
is raised up 400 mm above the patio, the top of the winding is at
1.2 m.  So Mike G3XDV was correct when he suggested that the
length of my loading coil might be a significant proportion of
the overall height of the antenna (12 m).

Also, I seem to recollect that some of the discussion involved excess
turns at the "hot" end (top) of the loading coil.  I wonder what might
have been the outcome if you had removed them, rather than simply
shorting them?

In fact, I eventually did just that!  I removed all of the excess
turns.  But even after having done so, I found no significant
difference in the antenna current.  I got the same results,
whether the excess turns were:
- left connected, but open circuit;

- physically removed from the coil former.

So, with Laurie's help, my next line of inquiry is to see if Mr
Stray Capacitance stole the 400 mills . . .  (It appears that
Eddy Loss has a good alibi.)

Regards to all,
Steve GW4ALG