I concur with Rik that this is not an India Office machine. May have been used in Palestine or Egypt by Indian troops.
There was a steel plate between the rear wheel and this type of air cleaner, much like the one on the left hand front fork of a Big4 to deflect excessive dust from the rear wheel.
There is one such aircleaner still aroud but I have not been able to trace it. Hussein sold it to "an Englishman" some years ago.
Rather annoying as it is probably lying around uselessly.
I would really like to see more details of it and obtain dimensions. I made a number of guesstimations but would like to have it correct.