Hembury was on a roll and ready to play his second card. “Last week, I spent a number of hours examining the contents of Box 1321 and now I totally understand why you tried so hard to keep them secret. The original documents and photographs chronicle the story of Adolf Hitler, Martin Bormann and Eva Braun’s safe passage from Germany to Argentina by boat. Also included are forged birth and death certificates that show their change of identity.”

Once again, Hembury paused to see if either man wished to speak but it was clear he had a captive audience, so he ploughed on. “They assumed the surname of Franklin. Adolf Hitler was your father, Mr Franklin.”

Hembury, for the first time, looked directly at John. “And your grandfather.”

Still, neither man spoke. They just stared back grimly at Hembury, who was now relishing the encounter.

“I even got to hold seven of Hitler’s war medals, including the coveted Iron Cross. But the most revealing insight into their secret existence after the war came from two reels of 8-millimetre film that show them in situ at their home in El Calafate. Trust me, it was far better than anything you’ll find on Netflix. Some parts of the film show Hitler and Bormann entertaining other prominent Nazis who also escaped to South America. But my favourite scene from all the remarkable footage will be of special interest to you, Mr Franklin, as you star in it. It shows you, along with your mother, celebrating your fifth birthday at a large party in the garden at El Blondi. I’m sure you must remember it.”

John Franklin was clearly struggling to hide his emotions and he looked distraught as Hembury continued with the onslaught. His father was desperately trying to work out a strategy to counter the relentless attack but it was all unravelling too fast.

“What do you want, lieutenant?”

Hembury was buoyed by this first sign of concession and decided it was time to play his third card. “I’ll let you know that shortly, but I haven’t finished yet, because I’m about to come to the biggest secret of all.”

Once again, Hembury switched his eyeline directly to the presidential candidate. “One that not even you know.”

John Franklin’s eyes flicked for a moment to his father, who acknowledged the look and had a mystified expression on his face.

“One of the death certificates we found in the box was a double forgery. Not only was the identity of the person a lie but the documentation of their death was an even bigger one.”

Richard Franklin guessed what was coming next and avoided any further eye contact with his son.