In Biggles Hunts Big Game, Mr Black was an operative of the international counterfeiting gang led by Kravas. Black appeared to manage the gang's affairs in London. One of his tasks was to recruit pilots for Stellar Skyways, the front airline operated by the gang. When Tug Carrington, at Biggles' behest, inserted an advertisement seeking a job as a pilot, it was Black who called up Tug, asking him to attend an interview at the Regency Hotel, Piccadilly. When Tug first saw Black, he observed that he was in his mid-forties and was the "typical town business-man type", well-groomed, keen-faced and with a brisk manner.
Black's chief concern during the interview with Tug was to ascertain that the prospective pilot recruit was impoverished enough, and therefore willing enough, to do whatever he was told without telling anyone and without asking too many questions. Whether the recruit was technically competent was left to the chief pilot, Ivan to determine. In interviewing Tug Carrington, Black also inserted the veiled threat that two pilots who had tried to betray the activities of Stellar Skyways had met with unfortunate accidents.
At the end of the book, Black was arrested at the International Pilots' Club during the general round up of the gang. Considering that Mr White was a cover name for the gang leader whose real name was Kravas, it is possible that Mr Black was also a cover name.