H. R. H. Princess Margaret, wearing the uniform of Commandant-in-Chief of the St. John Ambulance Cadets, leaving the Central Hall after the inspection.H. R. H. Princess Margaret makes her first public appearance in the uniform of Commadant-in-Chief of the St. John Ambulance cadets when she addressed cadets and watched competitions at the central hall, Westminster, London. October 22, 1948. (Photo by Sport & General Press Agency Limited)