Marshall Houts in his book Kings X, also titled Who Killed Sir Harry Oakes, asserted that American gangster, Meyer Lansky, sent henchmen to the Bahamas to intimidate and even assault Oakes but not to kill him during a secret late night meeting away from the Oakes mansion. It was alleged that Lansky was upset that Sir Harry was opposed to a casino being opened in the Bahamas. The murder was supposedly not intended and that Oakes body was returned to his home. The author further asserted that Oakes friend and colleague, Harold Christie, was working with Lansky and a participant in the murder.
The theory sounds like fiction.
James Leasor in Who Killed Sir Harry Oakes somehow ties together the burning of the liner Normandie in New York Harbour in 1942 and the Allied landings in Sicily.
John Parker in King of Fools added further to the involvement of Meyer Lansky. He suggests the investigating Miami detectives were on the mob payroll. He further suggests the Duke of Windsor had business connections with Lansky.
Charles Higham in The Duchess of Windsor: The Secret Story as set out in Wikipedia:
His conclusion in the second edition is that Oakes was murdered by an African ritual specialist from South Florida, who had been hired and brought into Nassau by airplane on the day of the murder by Harold Christie, a Bahamian mulatto business associate of Oakes. Christie and Oakes, the much wealthier man, had been friends and business partners for many years, and Christie had facilitated Oakes' move to the Bahamas. The two had apparently fallen out shortly before Oakes' death, because of Christie's dealings over the sale of Bahamian property on the island of New Providence, which was scheduled to be used for a new airfield by the Royal Air Force, a project of which the Duke would certainly have been aware and involved with since it had important strategic and economic implications, and would involve large expenses.
It sounds even wilder than the Lansky theory.
James Owen in A Serpent in Eden returns to Alfred de Marigny being the alleged murderer though he was acquitted at trial. He asserts he had seen documents in the British National Archives not publicly released.
Owens is another author reaching for a theory.
John Marquis in his book, Blood and Fire: the Duke of Windsor and the Strange Murder of Sir Harry Oakes rejected the Lansky theory and considered the murder was brought about Bahamian businessmen, including Christie, who feared Sir Harry was moving his fortune to Mexico.
De Marigny in his book A Conspiracy of Crowns said:
``In my mind there is no doubt whatsoever that Harold Christie should have been tried and hanged for the murder of Sir Harry Oakes. While hired hands acted for him, it was Christie who ordered the fatal act committed that turbulent night in Nassau.``
He further concluded the Duke of Windsor was one of the conspirators against him.
I think Marquis is closest to the truth but I do not think there was any Bahamian conspiracy. I think it was Christie acting on his own. He was staying in the house that night. It is probable that he was facing default issues over loans with Oakes. He was the suspect with best access and best motive. He also implausibly said he heard nothing of the murder a short distance from his bedroom.