Born in Tangier of a French father and an Arab mother, Dubroc had been a criminal all his life. He joined the French Foreign Legion in order to evade the police but had deserted. When in Paris, he had joined a Brand's gang which the French police believed was smuggling arms through Tangier to rebels in Algeria.
The French police arrested Dubroc but allowed him certain liberties when he offered to reveal the name of the gang leader. Dubroc took the opportunity to escape and thereafter made contact with his gang. The gang decided to fly him out to Britain, ostensibly to evade the French police but in reality to prevent him fronm talking.
The gang's pilot, Leroux was asked to pilot the gang's Aubert Cigale-Major with Dubroc and gang leader Louis Brand onboard from France to Brand's residence Dawfield Manor in Hampshire. Both Brand and Dubroc wore parachutes and planned to jump into Dawfield Manor rather than having the aircraft land. During the flight, somewhere over the New Forest, Brand asked Leroux to simulate an aircraft emergency and call to Dubroc to jump. Dubroc had complied and had fallen to his death because his parachute cords had been cut.
According to accounts given by Leroux and Brand, it was Dubroc who had cut the parachute cords himself. However they differed in what happened next. Brand asserted that it was Leroux who, in giving them out, got them mixed up, with Dubroc getting the tampered parachute. Leroux, on the other hand, held that Brand had seen the tampering, and that Brand had deliberately switched the parachutes, with Dubroc getting the damaged one.
Leroux believed that Dubroc had cut Brand's parachute because he planned to kill him and rob him of a large sum he was carrying to Britain, the proceeds of an arms deal. However the parachutes were somehow switched and Dubroc fell to his death.
Dubroc's parachute was found by the farmer's boy Len Betts, whose Father called Scotland Yard. Biggles and Gaskin swept the surrounding area and so found Dubroc's body. A tattoo on his left forearm in blue, partially erased, with the French word "destin" identified him as French. Using this feature plus a scar on above his right eye, Marcel Brissac was able to identify him as the fugitive the French police was hunting for. Apparently the tattoo mark was something Dubroc had obtained while in the Foreign Legion. He later regretted it and tried to remove it but without success.
The discovery of Dubroc's parachute and later his body was the beginning of a trail of clues which led eventually to the destruction of the gun-running gang.