Not specifically Wally. We seem to have started off earlier in the Middle East & have drifted into India, which is the correct area for the use of this flag.
Basically "native troops" black disc yellow flag - any theatre, "British troops" red disc yellow flag - but only when in India. Various religions & castes had different requirements & expectations for the processes that I won't go into in detail. Separation of 1 & 2, use of water rather than paper etc. All these sensitivities were encompassed in the Regulations.