Danny's nice re-working of the 'DR' photo (re-copied to here)reminded me of a report in Henk's archive where an Officer Commanding an R.Sigs. unit at Catterick gave his views on DRs and Drivers.
We tend to think of DRs and Motorcyclists as being almost the ultimate warrior but apparently this view was not universally held.
"...those chosen and trained to act as drivers and DRs are those not clever enough to tackle other jobs..." 
Imagine if this comment had reached the ears of those signing up for the 'Motor Cycling' recruitment scheme.
It's clear that some officers were missing being paid to ride horses.
It is surprising that in an age when the radio was not entirely reliable (or secure) and when telegraph lines could easily be cut by shelling etc. that more attention was not given to the D.R. message service where the buck eventually stopped Perhaps such blindness to the importance of communications and an over reliance on 'new' technology contributed to our rather poor performance prior to Dunkirk...and possibly after.
Of course it is possible that a staggering 50% shortfall in operating efficiency was compensated for by having 50% more DRs than were actually required!....Ian
email (option): julie@wright52.plus.com