Video: 20 years on from the collapse ITN On looks at the reasons behind its existence and constraints on freedom.

Elsewhere in the city, Germans will remember the 136 people killed trying to cross over from 1961 to 1989; candles will be lit, and 1,000 towering plastic foam dominoes placed along the wall’s route will be tipped over.

On November 9, 1989, East Germans came in droves, riding their sputtering Trabants, motorcycles and rickety bicycles. Hundreds, then thousands, then hundreds of thousands crossed over in the following days.

The party lasted four days and by November 12 more than three million of East Germany’s 16.6 million people had visited, nearly a third of them to West Berlin, the rest through gates opening up along the rest of the fenced, mined frontier that cut their country in two.

Sections of the wall were pulled down and knocked over. Tourists chiselled off chunks to keep as souvenirs. Tearful families reunited. Bars gave out free drinks. Strangers kissed and toasted each other with champagne.

Klaus-Hubert Fugger, a student at the Free University in West Berlin, was having drinks at a pub when people began coming “who looked a bit different”.

Customers bought the visitors round after round. By midnight, instead of going home, Fugger and three others took a taxi to the Brandenburg Gate and scaled the 12ft wall with hundreds of others.

“There were really like a lot of scenes, like people crying, because they couldn’t get the situation,” said Fugger, now 43. “A lot of people came with bottles” of champagne and sweet German sparkling wine.

The wall the communists built at the height of the Cold War and which stood for 28 years is mostly gone. Some parts still stand, at an outdoor art gallery or as part of an open-air museum. Its route through the city is now streets, shopping centres, apartment houses. The only reminder of it are a series of inlaid bricks that trace its path.

Checkpoint Charlie, the prefab that was long the symbol of the Allied presence and of Cold War tension, has been moved to a museum in western Berlin.

Potsdamer Platz, the vibrant square that was destroyed during the Second World War and became a no man’s land during the Cold War, is full of shops selling everything from iPods to grilled bratwursts.

In an interview in Moscow former Soviet leader Mikhail Gorbachev said the collapse was a catalyst for peace.

“No matter how hard it was, we worked, we found mutual understanding and we moved forward. We started cutting down nuclear weapons, scaling down the armed forces in Europe and resolving other issues,” he said.

It all began with a routine late afternoon news conference.

On November 9 1989, Guenter Schabowski, a member of East Germany’s ruling Politburo, casually declared that East Germans would be free to travel to the West immediately.

Later, he tried to clarify his comments and said the new rules would take hold at midnight, but events moved faster as the word spread.

At a remote crossing in Berlin’s south, Annemarie Reffert and her 15-year-old daughter made history by becoming the first East Germans to cross the border.

Reffert, now 66, remembers the East German soldiers being at a loss when she tried to cross the border.

“I argued that Schabowski said we were allowed to go over,” she said. The border soldiers relented. A customs official was astonished that she had no luggage.

“All we wanted was to see if we really could travel,” Reffert said.