Harry Hawker suffered from tuberculosis of the spine. The autopsy report states that an abscess near the spine had burst.
I believe it is more than likely that the abscess burst in the crash and that the fire was the cause of the crash. Hawker rode to the aerodrome on a motorcycle which would probably not have been possible with a painful spine.
In many years of collecting I have seen very few Harry Hawker autographs. I have copies of these books: Hawker by Blackmore, Our Atlantic Attempt by Hawker and Muriel Hawker's biography of her husband. Does anyone know of other books about Hawker?