When Biggles first met Del Grikko, Johns provided one of his eloquent word pictures of him. Del Grikko was described as tall, powerfully built, clean shaven and of early middle age. He was of uncertain nationality but his skin was "of that curious smooth texture and indefinable tint peculiar to countries bordering on the eastern Mediterranean." His har began low on the forehead and was jet black and "gleamed with an oil dressing". Biggles observed that when younger, Del Grikko might have been considered handsome but pouches under the eyes and sagging jowls, the result, it seemed, of too much good-living and too little exercise, "destroyed any illusion of good looks." but significantly, Biggles noted that a "prominent nose" and "firm mouth" suggested a strong character, a man who was not to be trifled with.
When Ginger turned up at the bar after tailing a member of the drug gang, Del Grikko had him drugged and brought into his office. He told Ginger he knew about him following his man because his taxis were equipped with radio. Del Grikko angrily asked who had sent Ginger but Ginger would give away nothing. He had, however, developed the impression that Ginger had been sent by Max Bronnitz, suspected to be a rival to the drug gang. Later that night, Bronnitz was murdered by Alfondez, a member of the drug gang. Alfondez claimed he was acting under orders, presumbly issued by Del Grikko.
Del Grikko was equally ruthless with Biggles who barged into his office seeking to extract Ginger. Knowing he outnumbered Biggles and had the upper hand, Del Grikko took out an automatic and instructed his bodyguard Louis to ask the band in the bar to make as much noise as possible. Del Grikko was getting ready to shoot Biggles and Ginger but Marcel Brissac intervened just in time. On seeing Marcel, Del Grikko's demeanour changed, and he was all friendliness, allowing Biggles and Ginger to leave.
Del Grikko's fate at the end of the book is not revealed but it is presumed that he was rounded up with the rest of the gang.