Like every Thursday night back then, Angela Merkel was relaxing in an East Berlin sauna on the night of November 9, 1989 as the Berlin Wall fell, dreaming of tasting oysters in the West.

The future chancellor of Germany was indulging in a favourite German winter pastime on the night that led to German reunification.

"Every Thursday, I would go to the sauna with a friend," Merkel, in power since 2005, recounted to Berlin schoolchildren a few years ago.

At the time Merkel was a 35-year-old physicist at the East Berlin Academy of Sciences.

Born in Hamburg but raised in the German Democratic Republic (GDR), she was already divorced from the first husband whose name she still uses.

She lived then in a two-room flat in Prenzlauer Berg, these days a favourite haunt of trendy young professionals.

Before her sauna session on November 9, Merkel called her mother Herlind Kasner, who lived around 80 kilometres north of the capital.

She had just heard that East German citizens were free to cross the border.

But in those confusing first hours as the barriers opened, no-one could quite believe it was really happening.

"I didn't really understand what I was hearing," Merkel has said.

Oysters at Kempinski's

The family had "an in-joke" at the time that Merkel would take her mother "to eat oysters at Kempinski's", a high-end hotel in the West.

"Watch out mum, there's something up today," she warned her mother, before hanging up and heading to the sauna.

German Chancellor Angela Merkel leaving a tribute in a preserved segment of the Berlin Wall in 2014
German Chancellor Angela Merkel leaving a tribute in a preserved segment of the Berlin Wall in 2014 AFP / JOHN MACDOUGALL

While she was enjoying the heat, history shifted up a gear.

The first border crossing opened not far from Merkel's flat, and champagne corks popped as people celebrated the end of the division that had scarred Germany and Europe since the Second World War.

One of the crowd

On her way home, she saw people on their way to the crossing.

"I'll never forget it, it was maybe 10:30 pm, or 11, or even a little later," the chancellor recalled.

"I was alone but I followed the crowd... and suddenly we found ourselves on the western side of Berlin."

Just another member of the crowd, Merkel drank her first can of Western beer in a flat rented by total strangers.

But the thought of her alarm sounding in the morning dogged the scientist even through that historic night, sending her home long before the festivities were over.

Soon after, Merkel left physics behind to begin a career in politics.

In 1990, she was elected an MP for the Christian Democratic Union (CDU), then led by Helmut Kohl.

The following year, Kohl named her a minister for the very first time.

But in all the years since, Merkel never got to fulfil her pre-1989 wish.

"I never went to Kempinski's to eat oysters with my mother," Merkel has admitted. Her mother died earlier this year, aged 90.