From AARSE
""During WWII many airborne soldiers were given permission by their CO to wear 'Wings on Chest' this unofficial accolade was normally granted for operational jumps (in SOE this was normally granted after one operational jump). In the Airborne, RSR and SAS at the CO's discretion. At an investiture King George VI asked a couple of SAS Sgts if they were pilots - no sir came the reply we're in the SAS. The King ruled that only the RAF and Army aircrew could wear their brevets on the chest. This resulted in a long wrangle between the airborne, SAS, the War Office and the Palace - with Montgomery lining up with the Airborne Forces, after a long time there were perhaps half a dozen serving wartime SAS members who were allowed to carry on with the practice. In the 1970s in Rhodesia the Rhodesian SAS reinstated the practice of Wings on Chest (WOC) an honour that was valued more than some of the medals."
Wings on Chest - Airborne - WW2 Talk