JANUARY 1989: I am standing with a group of German teenagers in the debating chamber of West Berlin’s city hall. Around us are the chairs of the council members.

The seats over there, our guide points across the chamber, are for the representatives from east Berlin: “For when our city is no longer divided.”

I am sure I was not alone in thinking: “Yeah, like that’s ever going to happen.”

I had seen the Wall, a great, graffiti-covered monstrosity running through the heart of the city. I had stood on a platform outside the Reichstag and looked out over the expanse of noman’s- land, across the reputed site of Adolf Hitler’s bunker and into the East. I had seen the crosses in memory of those who had died trying to get to the promised land of the West. That wall did not look like it was coming down any day soon.

I was visiting Berlin with a coach party of German 14 and 15-year-olds from a small town near Heidelberg, where I was spending a year as an English language assistant. We had travelled as far as we could in West Germany before crossing into the East for the last stretch of motorway before Berlin.

A long wait at the border, during which time the teenagers had been told to put away all their Western magazines and music, had heightened the sense of entering the unknown, even if initially we would only have a fleeting impression of the East as we made our way to West Berlin.

With that party of schoolchildren a few days later I made the journey across the great divide, into East Berlin. I have few clear memories of the day other than an overwhelming sense of fear. After all, these were communists, the evil shadowy force we in the West had to fear.

The Stasi (East German security police) might not have been well-known in the West at that time, the extent of their reach only becoming truly apparent after the fall of the Wall, but I had been warned to be on my guard against unofficial – and most definitely illegal – street money exchangers. I had been told some of these were plants who could spot a Western tourist at a hundred paces.

So I viewed everyone with suspicion – including a border guard who to this day has no idea of the anxiety he caused me.

Taking my passport, he looked at me and smiled. “This can’t be good,” I thought, as every spy thriller I had ever read rushed unbidden into my head. “I’m never going home.”

Pointing to my name, he said: “Just like the Ford Motor Company” and handed back my passport. I nodded, smiled – and got back over the border as fast as possible.

That evening, back in the familiar hustle and bustle of the West, one 14-year-old summed up the day very simply. “Nobody smiled,” he said.

ELEVEN months later, I am watching the BBC news with a sense of disbelief. The Wall, that very solid symbol of the divided Europe, had been breached – and on such a key date in German history. It was on November 9, 1918 that Kaiser Wilhelm II was forced to abdicate, an act that led to the signing of the armistice that ended the First World War two days later.

It was on November 9, 1938, that Nazi gangs attacked Jewish-owned shops and synagogues in a night of violence that has gone down in history as the Reichskristallnacht. And now, on November 9, 1989, the gates had opened between the East and the West to make Germany whole once more.

During the summer of 1989 I had watched on West German television as East Germans set up camp in the Federal Republic’s embassy in Prague, as the demonstrations for the right to travel had grown in the East, and as then Soviet leader Mikhail Gorbachev had spread his message of glasnost and perestroika during a highly successful tour of West Germany, with one political cartoonist, drawing on John F Kennedy’s famous one-liner “Ich bin ein Berliner”, capturing the mood with the words “Ich bin ein Westerner” above a drawing of Gorbachev.

I had spoken to people who had fled the East, knowing they could never go back, never visit their families and loved ones, never return to the haunts of their youth – and who would not divulge how they had got out for fear of compromising an escape route that was still in operation.

It was the stuff of spy fiction made real.

In subsequent years, I met young East Germans who had been on national service during November 1989, some of whom had been on border patrol during that fateful week and reacted in disbelief when told the Wall had come down, and others who had been told to sleep in full kit in case they had to confront their own countrymen and women.

I met East Germans who looked at me with incredulity when I spoke of how we had lived in fear of the Russians sweeping through East Germany to invade the West.

“That’s not how it was,” I was told. “The Americans were going to come through West Germany and invade us.”

And I met a young girl who told me how her brother had managed to leave the East and that she had not expected to see him ever again. Her matter-of-fact words belied the true enormity of what that must have meant to her.

December 1992, I am back in Berlin for the first time since that January trip. The Wall has gone, Germany has reunified, and I am there to make a journey that nearly four years earlier I never thought I would make.

Beginning at Alexanderplatz, the East Berlin square I first saw on that cold, grey, bitter January day, I walk along Unter den Linden and through that most iconic of Berlin symbols, the Brandenburg Gate, to the Reichstag, where in 1989 I had stood on a platform looking into the East – and in a few steps completed a journey from East to West for which during the 40 years of division so many had given their lives.

■ Tomorrow: Growing up behind the Wall