Not that sure, but I think there use to be an RAC box on A23 northbound at Pyecombe, near Brendon Riding School.

Initially this looked more like a posed photo for advertising purposes rather than an actual patrolman. The box and surrounding area were far too neat and newly painted to be one that was in general use. My father was the RAC patrolman covering Pyecombe to Crawley for over twenty years, initially on a 500cc side valve Norton combination, then in an A35 van, and finally he had a van based on an Austin Mini. In searching for a photo of him to attach, I found one of him at his retirement dinner in 1970. Although now much older, one of the other uniformed patrolmen or bosses gathered round the table bears a remarkable likeness to the other patrolman shown in your picture.