Well 1956 was the time of Suez and we had the petrol rationing into 1957 so road motor sport (rallies) was more or less on hold.
Neil Freedman solved the problem for the UHULMC by inventing the "Miglia Quadrato" which was a night navigation event held in the City of London (known to its friends as "the square mile", hence the name of the event) working from the 6" to the mile (1:10,000) map with competitors covering about 6 miles.
Won't be that event as the photo looks like daylight, but perhaps it is on a similar fuel-crisis event.