The ambassador and other embassy representatives were among the first to lay wreaths at the memorial.
A number of veterans came from Russia to participate in the ceremony.
The event is regularly organized by the Soviet Memorial Trust Fund that invites veterans, officials from former USSR countries, local officials and private citizens.
The memorial was opened in London on May 9, 1999. The special ceremonies are held next to it thee times a year, on May 9 to mark the Victory Day, on January 27 to honor the victims of the Holocaust and on Remembrance Day, observed in the United Kingdom in mid-November to honor the memory of all war victims.