In 2005 Greg Hallett wrote a book, Hitler Was A British Agent, alleging that Adolf Hitler was actually an agent working for the British government. This book is highly criticized because it offers absolutely not a single of shred documentary evidence to support its allegations. Rather, the claim is based on circumstantial evidence from one Bridget Dowling, allegedly the one-time wife of Adolf Hitler's half-brother, Alois Hitler.
Bridget claimed that Adolf had come to Liverpool in 1912-13, and stayed with her and her husband. However she never made a claim that Adolf Hitler became a British agent during this time. Rather, all of her claims concerning Hitler are comparatively innocuous. It is only Greg Hallett who extends this supposed circumstance into his own pet theory. Even worse, most mainstream historians familiar with the story believe that the Bridget Dowling book is a fraud in the first place. Dowling's own daughter-in-law is recorded as having said that Bridget's book was fanciful. Dowling was unable to sell the manuscript and most historians dismiss the work as being a fabrication written in an attempt to cash in on her famous relation.
In his book, Mein Kampf, Adolf Hitler never even mentions having either a brother or a sister. He does relate the entire story of his life from the time he was a boy through to adulthood, and along with other details he discusses his birthplace, his father's occupation, and his relationship with both of his parents at length, but he does not give their names.
Additionally, Adolf Hitler was in Munich when the First World War broke out. He arrived in Munich in the Spring of 1912 (Mein Kampf, p. 80) and he was still there when the war came (p. 96). There is no reason to doubt any of Hitler's account of his life in these pages. He had absolutely no reason to lie (even if he had really visited London), and the history of the surrounding period and what is known and documented concerning Hitler's wartime record help to prove the veracity of his account. My only conclusion is that Bridget Dowling was a liar attempting to cash in on what was scarcely a relationship, if indeed it existed at all. And Greg Hallett is a bigger liar, attempting to cash in by compounding the lies of others with those of his own making.