When Hans Schulze was imprisoned in Communist East Germany in the 1980s, he never imagined he would want to return if he was released. But now he regularly unlocks his old cell door to show tourists what life was like in a jail run by the Stasi, the secret police.
A West German who was responsible for his chemical company's business in the East, Schulze was on his way to a trade fair in the East German city of Leipzig in 1986 when he stopped at a motorway service station and met a woman by chance.
Schulze, now 66, was fascinated by the well-dressed woman and they began a relationship. The East-West dimension of their liaison gave Schulze a thrill, but to this day he does not know for sure whether she loved him or was just using him.
"I didn't know that she was an unofficial Stasi informant," said Schulze, who gives tours of Berlin's Hohenschönhausen prison, now a museum and memorial, where he spent some of his 13 months behind bars.
"It was only later, when the accusation of spying was raised, that everything appeared in a different light," he recalls.
Schulze found out after he had became romantically involved with the woman that her husband, from whom she was separated, worked for the Stasi. But he did not grasp the full extent of her involvement until the media reported on her Stasi files in 2009.
Under its foreign intelligence chief Markus Wolf, the Stasi perfected the use of "Romeo spies" – agents who used their personal charms to ensnare vaulable sources of Western intelligence.
Unbeknown to Schulze, his lover had been tasked by the Stasi with picking up solo travellers and business people from the West. She told him she wanted to flee to the West and Schulze still isn't sure whether that was her personal desire, or whether the Stasi wanted her to continue working for them in the West.
Three years before the fall of the Wall, Schulze was arrested at the border as he tried to leave the East. A letter the woman had written about her husband's work was found in his car, as was some money she wanted Schulze to take to the West.
Schulze was accused of spying and a day later his lover was arrested, though he does not know what the charge against her was.
East German authorities ultimately withdrew accusations of spying, subversive human trafficking and betraying state secrets agianst him – which would have triggered a long prison term – and he was ultimately sentenced to two and a half years in prison for currency crimes and helping prepare an illegal border crossing.
Schulze thinks his status as a West German meant that he was probably treated better than other prisoners at Hohenschönhausen, where psychological interrogation methods were brutal.
Helge Heidemeyer, director of the Hohenschönhausen memorial, explained: "The people who were imprisoned here were completely depersonalised. They were only addressed as numbers and they were subject to a daily routine that didn't allow them to come into contact with anyone except the guards, who kept an eye on them at regular intervals.
"At the same time, they faced unpredictability. They never knew when they would be taken to their interrogator. They never knew what would happen with them and when."
Schulze added: "You have to imagine living through almost nine months of remand here, always being accused of spying until they ultimately change that accusation by saying, oh we're taking that back and we'll make it something else, which is much more harmless. I can tell you it really hits you hard. And I know now that they did it on purpose.
"Of course these events have had a big impact. That period of time still affects me to this day and that's why I give tours here now, to pass on the message."
He was transferred to another prison before his release in October 1987. His lover, who had spent her imprisonment working in the kitchen at Hohenschönhausen, was freed a month later. They saw each other in prison but Schulze said their relationship ended around the time they were released, and after reunification in 1990 she became a car saleswoman and hotel director in the West.