Comments by R.N.E. (Top 1 by date)

I've used the corrected ProcessStartInfo code as suggested but without the hardcoded path and it works fine (presumably using the PATH environmental variable as I'd originally hoped):
test.StartInfo = new ProcessStartInfo("R", "CMD BATCH /usr/Scripts/program /usr/Scripts/output");
I think I must have copied and pasted the original version from somewhere without properly understanding what I was doing, which is always unwise! Anyway, I am currently trying to accept this as the solution.
Many thanks
RNE