I am fairly certain that in his book 'Thrilling the Million' that Tom Stenner credits Johnny Hoskins with the start of speedway at West Maitland in December 1923. It's hard for me to be certain now because it was many, many moons ago that I read the book which was published around 1934.
One thing that still stands out in my mind from the book is an amazing crash photo taken at High Beech and featuring, so I recall, Ron Johnson and Bobby Blake.
Be that as it may, we still need to trace one of Johnny's early books to see if he has anything to say on this ongoing and engrossing topic.