Because of the atmosphere of authenticity that the scripts evoked and the liberal use of "spook" jargon, there has been speculation that Mackintosh might have been a former operative of SIS or had, at least, contact with the espionage community. This has extended to speculation that his disappearance was no accident or had to do with a secret mission he was undertaking. There is a possibility that Mackintosh may have been involved in intelligence operations during his time in the Royal Navy, but no conclusive evidence has surfaced. When asked, Mackintosh himself was always coy about whether he had been a spy. It is possible that this information prompted the thriller writer Desmond Bagley to name-check Mackintosh as an intelligence agent in his novel "The Freedom Trap".