Russian tycoon Boris Berezovsky, a former mathematician and government official, made his fortune in the post-Soviet Russia of the 1990s.
He profited from gaining control over various assets, including the country's main television channel, Channel One. In 1997, Forbes magazine estimated Berezovsky's wealth at $3 billion.
Berezovsky was at the height of his power during President Boris Yeltsin's years in office, and Berezovsky was made deputy secretary of Russia's security council.
He helped form the Unity party and became a parliament member. Berezovsky was initially a supporter of President Vladimir Putin, but the two clashed soon after Mr. Putin's election in 2000. Berezovsky then became a vocal Kremlin critic.
In late 2000, Russian authorities demanded that Berezovsky appear for questioning, but he did not return from abroad. Instead, he moved to Britain, where he was later granted political asylum.
A Russian court convicted him in absentia of economic crimes.
The government took over his television assets and appropriated his other holdings in the country.
In Britain, he socialized with other Russian exiles critical of the Kremlin, including Chechen leader Akhmed Zakayev and former Russian spy Alexander Litvinenko.
Berezovsky publicly campaigned against Mr. Putin, whom he accused of suppressing freedoms in Russia.
In 2012, Berezovsky lost a $6-billion legal battle against Chelsea Football Club owner and fellow Russian Roman Abramovich, whom he accused of blackmail and intimidation related to assets in a Russian oil company.
Recent reports say that high legal costs forced Berezovsky to start selling his assets, including a valuable Andy Warhol painting.