The real life incident that this story was based on, happened when David Taylor was a student vet. A female elephant at Belle Vue Zoo had been on anti-arthritic drugs for some time, and when these failed to alleviate the pain, the only answer was to euthanase her. They did this by anaesthetising her, and then using carbon monoxide from a motorcycle to finish the job. This caused David Taylor to question how exotic animals could be better treated.