The Dennis Wheatley 'Museum' - Researching the Occult

DW refers to Alexander Cannon's 'The Invisible Influence' (first published in October 1933) in 'The Devil Rides Out'. In Chapter III, 'The Esoteric Doctrine', Rex says :

"'The Invisible Influence'. I've certainly heard that phrase somewhere before."

and the Duke replies :

"No doubt. A very eminent mental specialist who holds a high position in our asylums wrote a book with that title and I have not yet asked you to believe one tenth of what he vouches for."

Dr Cannon (1896-1963), who referred to himself as 'His Excellency Sir Alexander Cannon', had an interesting career. Born in Leeds, he received and MD and a PhD, and in the late 1920s and early 1930s he was vice president of the Hong Kong Medical Society and medical officer in charge of prisons. He also served for a time as British Consul in Canton. He studied occultism and yoga and travelled in India, China and Tibet. Although he wrote various books before and after, The Invisible Influence is his best known work. It is written as a series of conversations between Cannon and a series of mystics, yogis and other sages, and includes anecdotes of crystal gazing, levitation, hypnotism, distant touching and other psychic phenomena.

On his return to England Cannon worked in a mental institution and was briefly dismissed, although he was re-instated after he went to court for wrongful dismissal. He then set up a highly lucrative consultancy in Harley Street, and he is reputed to have been consulted by King Edward VIII among others.

Referring to the book apart, DW may have got the idea for one of the most memorable episodes in 'The Devil Rides Out' from Cannon. The Angel of Death who appears as the invisible rider on a great black stallion in Chapter XXVII of 'The Devil Rides Out' (or as a skeleton in armour on horseback in the 1968 film), is reminiscent of "the Angel of Death, the black rider on the black and fiery steed, who carried a fiery sword" that a black magician invokes to kill a famous judge in Chapter XI of Cannon's book.

References : 'The Devil Rides Out' Chapter III & XXVII.
'The Invisible Influence' ChapterXI
Phil Baker p 332.

Further reading : See the Wikipedia entry on Cannon.