unsuccessful referendum to unite Berlin and Brandenburg he had spearheaded with Stolpe. In 1999, news media first reported about a dispute between Diepgen and the U.S. Department of State over American demands for special security treatment for its new Berlin embassy not sought by other countries that had built embassies in the same area, including Britain and France. As a result, the construction of the embassy was delayed over several years by a dispute over how large a buffer zone it requires for security. Amid the revelations of the CDU donations scandal in early 2000, Diepgen opposed Angela Merkel as new chairwoman of the party. On 6 July 2000, Diepgen signed a treaty with Matheus Shikongo, the Mayor of Windhoek, on a twin city partnership between the two municipalities. In September 2000, Diepgen pardoned two former members of the East German Politburo, Günter Schabowski and Günther Kleiber, who were jailed for their role in East Germany's shoot-to-kill policy at the Berlin Wall. In June 2001, the Social Democrats withdrew from Diepgen's administration and tabled a motion of no-confidence in Diepgen, accusing him of mismanagement and corruption. Diepgen resigned, and Klaus Wowereit became acting mayor. Ahead of the 2002 federal elections, Diepgen resigned as chairman of the CDU in Berlin after having failed to secure the top position on the party's list for the elections. He was succeeded by Joachim Zeller. Life after politics Following his resignation in 2001, Diepgen joined the Berlin office of German law firm Thümmel, Schütze & Partner. In addition, Diepgen has held various paid and unpaid positions, including the following: Ernst Reuter Archives, Member of the Board of Trustees Evangelical Academy Berlin, Chairman of the Board of Trustees Friends of the Academy of the Arts, Member Gegen Vergessen – Für Demokratie, Deputy Chairman of the Board Konrad Adenauer Foundation, Member Otto Benecke Foundation, Chairman of the Board of Trustees Synanon Foundation, Member of the Board of Trustees Zoological Gardens of Berlin, Chairman of the Board of Trustees (since 2010) Diepgen was a CDU delegate to the Federal Conventions for the purpose of electing the President of Germany in 2017 and 2022. Controversy In 1986, Diepgen acknowledged accepting 50,000 West German marks, or about $21,000, from real estate investor Kurt Franke without having reported the amount as a party contribution as demanded by law. The Mayor later added that the total might have been 75,000 marks. As