World leaders join tens of thousands of tourists and well-wishers on the streets of Berlin celebrating the 20th anniversary of the fall of Berlin Wall.
Chancellor Angela Merkel, the first German leader to have grown up in communist East Germany, told a ceremony at the historic Brandenburg Gate that German unity was still incomplete, as the East lagged in economic growth.
The fall of the Wall led to the collapse of Communist power and German reunification; it became a symbol for the end of the Cold War.
On 9 November 1989 the East German Politburo member Guenter Schabowski announced that East Germans would be allowed to travel freely to the West, BBC News reports.
In the meantime, Gordon Brown insisted the tide of history was moving towards our ''best hopes'' as he attended a ceremony to mark the anniversary.
The Prime Minister insisted the events of 1989 showed that ''no abuse, no crime, no injury need endure for ever''.
He was speaking in Berlin alongside leaders including German Chancellor Angela Merkel, French President Nicolas Sarkozy, Russian President Dmitry Medvedev, and US Secretary of State Hillary Clinton.
Earlier, Ms Merkel and former Soviet leader Mikhail Gorbachev symbolically crossed one of the city's former fortified borders to cheers.
She lauded Mr Gorbachev, saying: ''We always knew that something had to happen there so that more could change here.''
Mr Brown said what happened on November 9 two decades ago, when travel restrictions were lifted and hundreds streamed into West Berlin, meant ''no one can ever again imprison a people who know what it is to be free,'' Telegraph.co.uk reports.
It was also reported, amid praise and joy, German Chancellor Merkel spoke of another November 9, even longer ago that, she said, should always serve as a warning.
She said that 71 years ago, the pogroms of Adolph Hitler's Third Reich opened the darkest chapter in Germany's history - the systematic persecution and murder of Europe's Jews and many other minorities. "That too we do not forget today," she said.
On November 9, 1938, on Kristallnacht, or The Night of Broken Glass, at least 91 German Jews were killed and more than 200 synagogues were destroyed by rampaging Nazi mobs.
Chancellor Merkel said the Nazi pogroms and the Berlin Wall serve as reminders, Voice of America reports.