The clue for 15 down is "Troops rally for Berlin make" 6 letters. The answer will be a make of car.
I have ?R?L?S and the word Drills comes to mind but I have been able to find no reference to a car maker named Drills in Berlin or anywhere else. Any suggestions would be much appreciated. The car could have been made at any time. Any suggestions would be much appreciated.
Many thanks to you both. You are both absolutely right. I had 21 across (1905/6 shorter chassis Rolls Royce Twenty) as "LEGAL" thinking of the LEGAL LIMIT whereas the correct answer is probably LIGHT which would indeed give the "T" for PROTOS.