A query about manure

Sir,

So, just who was the first person to say, “Whet the flag drops the bullshit stops”?

In Modern Times (March, 1999) Simon Taylor credits Sir Jack Brabham. I have read (I forget where) the same phrase credited to another driver (I forget whom). Yet I have always thought that it was the work of Frank Gardiner.

So, does anyone out there know just who did first coin this immortal phrase?

I am, yours, etc. David Fisher, Fearnhead, Warrington