The Berlin Wall anniversary is a reminder that people smugglers were once regarded not as the scum of the earth but as heroes.

Hartmut Richter was one. He fled East Berlin five years after the wall was built by swimming across one of the canals that separated the city.

He then helped another 33 people escape by smuggling them across the border in his car.

Twenty years on, he worries about what is called Ostalgie - nostalgia for the old East Germany.

The former German Democratic Republic has largely been romanticised in film, fashion and design. But Mr Richter warns that the worst crimes of the former East Germany have been too easily forgotten.

Deep in the Berlin suburb of Hohenschoenhausen lies the empty shell of a secret jail. It belonged to the Stasi, the feared East German secret police.

Mr Richter, a former prisoner, gives tourists guided tours. He says many officials of the Stasi have escaped punishment.

"Over here on your left, that's not a hallway, that's a torture cell where the ceiling's so low you can't stand up," he said.

He spent a year being interrogated in an isolation cell in the jail before he was moved to another prison in Potsdam.

He was charged with people smuggling and being an enemy of the state. But like so many other East Germans, his story begins in August 1961.

"Coincidentally or not, I was visiting my favourite cousin on August 13, 1961, in West Berlin," he said.

"As a 13-year-old, I watched as the wall went up, how people jumped out of windows.

"I returned to my parents after two days. At school the teachers told us about the anti-fascist protection wall that was built.

"I had to walk out of the classroom. I already pictured this so-called protection border more as a prison."

Five years later, Mr Richter made his first escape attempt. He was caught but released with a warning.

A few months later he got away.

"The first one who comes over helps the others to escape," he said.

Underestimated

Starting in the 1970s, the period of detente, East Germany opened its borders a little. They let West Germans visit relatives and friends in the East under the so-called transit agreement.

"When you drive across the border a few times, you realise 'wow, they aren't checking anymore'," Mr Richter said.

"Well what would happen if you hid a mate in the boot of the car and drive him out of the east?"

Mr Richter helped 33 East Germans escape but he says he underestimated the Stasi.

"They cross-referenced the transit lists with the number of defectors and eventually they realised every time I drove from east to west someone went missing. I only know all this from reading my Stasi file," he said.

"On the night of the 3rd or 4th of March 1975, I was driving back to the west with my own sister in the boot and at the border they yelled, 'Exit to the right, drive to the right'.

"And I said 'hang on a minute, I'm a transit visitor and you should let me pass'. And he said 'drive into the garage'.

"There were 10 border guards with weapons but were friendly, but then came the less-friendly sniffer dog into the garage.

"As the dog jumped onto the boot of the car, I was pushed against the wall with 10 machine guns pointing in my face and in the boot of the car was my own sister."

Mr Richter spent five years in jail. He endured lengthy interrogation and sleep deprivation. Eventually the West German government bought his release under a prisoner exchange scheme.

But back in the west, with the Cold War thawing, he felt disillusioned with what he saw as the apathy about the communist east.

So he staged protests to draw attention to the wall. He threw leaflets over into the East and even managed to steal a bed of nails from the death strip.

"I was surprised to read in my Stasi files that there were plans drawn up to kill me, wipe me out. That was shortly after I stole the bed of nails," he said.

"They planned to shoot me. They wanted me to make a second protest and then they would be prepared because the first action took them by surprise.

"So they tried to convince another former prisoner, who was working as a spy for the East, to convince me to steal another bed of nails and they would wait with snipers."

Disgust at nostalgia

Now Mr Richter helps former political prisoners apply for compensation. But he is angry that many former Stasi employees escaped punishment and now enjoy a healthy state-sponsored pension.

"It's unbelievable that former officers of the secret police receive a pension as high as officers of the German army," he said.

"It may be legally defendable but it can't be defended on ethical or moral grounds."

Twenty years on from the fall of the wall, he fears that a new generation is growing up that does not understand how oppressive it was to live under communism.

It was a country where everyone felt spied on, and most of them had reason to fear it. For Mr Richter, there is nothing to be nostalgic about.

"I think it's disgusting how East Germany is sometimes portrayed. Can you imagine if the history of Nazi Germany was glossed over like that? It would be an outrage," he said.

"It's a disproportionate response the way that the history is trivialised and romanticised. You can understand why people like me see this very critically."