Who is Paul Nielssen and Armando Bassi from Death in the Long Grass and what is their importance?

Paul Nielssen was a professional hunter and Capstick's associate during the period of time considered by the text. Bassi was Nielssen's Spanish hunting client. While the two men were hunting, Bassi wounded a lion which subsequently ran into thick cover. Nielssen followed up the lion, which doubled back and cut its own trail. The lion surprised Nielssen and bit him through the shoulder, knocking him down. It then began to savage Nielssen's leg. Bassi heard Nielssen's screams and ran into the cover, shooting the lion off Nielssen.