History's hit series Hunting Hitler has been exploring conspiracy theories about Adolf Hitler's death for three seasons.
Trekking around the globe, visiting Spain, Argentina and Chile, a team of journalists, ex-CIA veterans and army officers are determined to prove that Hitler didn't die in his Führerbunker in 1945.
The investigation's leader Bob Baer, a 21-year CIA veteran, said at the end of season one: "History is not fixed as we receive it. I will never stop searching for the truth, I never take facts at face value and I never will."
Season 3 is currently airing at 9pm on Mondays on History - BT TV channel 327/379 HD.
Here are five of the most shocking theories from the Hunting Hitler team.
1. The bunker mystery
The starting principle of the series is that the death of Hitler we have all read in History books - that he took his own life with wife Eva Braun - is a lie.
Russians raided the bunker and reportedly took the German leader's remains with them. However, the only DNA evidence available, a skull with a gun shot, belongs to a female.
"Until we have a corpse, it will be an open investigation," insists Bob Baer.
2. The escape from Germany
If Hitler didn't die in his bunker, then where did he go? The Hunting Hitler team believe that there were multiple escape routes, tunnels and possible methods for him to get out of Berlin - even when it was heavy attack from the Russians.
They have identified routes to potential flight exits, either at Tempelhof or a make-shift runway at the Brandenburg Gate. Potential destinations for the plane were either Denmark or Franco’s Spain, which would have provided refuge for the Nazi leader.
3. The U-boats theory
Most alleged sightings of Hitler after 1945 came in South America and not Spain, so the problem for the Hunting Hitler squad is how he could have travelled that distance safely.
The theory they develop is that he could have travelled via U-boat and the team discover in series two, evidence to back up the conspiracy.
During a visit to the Hotel Reina Cristina, the team find a direct link from the hotel, down a route of tunnels, which could have been used as a secret shuttle to take people secretly to the ocean.
4. Hitler was hidden and protected in Argentina
The right-wing Argentina Juan Peron was a Nazi sympathiser and could potentially have been an ally for Hitler. The Hunting Hitler team have discovered several possible buildings, hidden networks and eye-witnesses, which suggest that there were Nazis running operations from South America.
The mysterious military structures in the middle of jungles and connecting networks of towers and bunkers that they discover also plays into the theory that the buildings were being used to protect a high value target.
Burrowed tunnels into mountains, safe houses and sightings of senior Nazis close to Hitler help stack up some handy evidence for the investigation team.
5. The Fourth Reich theory
Perhaps the most outlandish theory from the Hunting Hitler team is that Adolf Hitler didn’t just go on the run, but that he was actually fully operational in South America.
They suggest that Hitler and the Nazis were developing a “Fourth Reich” from Argentina and that they were hoping to develop weapons of mass destruction to take out the United States.
Historians may be shocked by these suggestions, but the investigators still have the rest of season 3 to stake their claim.
Hunting Hitler airs Mondays 9pm on History.
History is one of 60 premium channels available on BT TV along with other channels such as E!, Comedy Central, Discovery and many more.