[1] According to the British journalist Robin Bruce Lockhart, who knew her personally, "she was, perhaps, the Soviet Union's most effective agent-of-influence ever to appear on London's political and intellectual stage".

[3] In 1911, she married Count Johann (Ivan) Alexandrovich von Benckendorff (1882–1919), a member of the Baltic German nobility, Second Secretary at the Russian Embassy in Berlin, and Gentleman of the Court.

[7] (Lockhart's book was made into an American movie in 1934, British Agent, starring Leslie Howard as "Stephen Locke" and Kay Francis as "Elena Moura".)

Budberg was widely suspected of being a double agent for both the Soviet Union and British intelligence and has been called the "Mata Hari of Russia", after the famous Dutch exotic dancer and accused spy.

[citation needed] She is known to have visited the Soviet Union at least twice after the 1920s: first in 1936 for the funeral of Gorky (which made people call her an agent of the NKVD) and again at the end of 1950, with a daughter of Alexander Guchkov.

[14] Budberg's older half-sister, Alexandra "Alla" Ignatievna Zakrevskaya (1887–1960), who married Baron Arthur von Engelhardt (1875–1909) in 1908 but divorced in 1909,[15] was the great-grandmother of Nick Clegg, the leader of the British political party the Liberal Democrats between December 2007 and May 2015, and Deputy Prime Minister of the United Kingdom from 2010 to 2015.