Mr Glushkov's friend Damian Kudryavtsev posted a tribute on his Facebook page, with a photo of of Mr Glushkov and the simple message: "Nikolai Glushkov 1949-2018".
Nikolai Glushkov was found dead by family and friends at his home in London on Monday, The Guardian reported.
Glushkov was subsequently charged with money laundering and fraud and served five years in jail in Russian Federation.
Glushkov's death came a week and a day after fellow Russian exile Sergei Skripal and his daughter Yulia were critically injured in a nerve agent attack in Salisbury. Whilst we believe we know the identity of the deceased, formal identification is yet to take place.
"At this stage the Met Police Counter Terrorism Command is leading the investigation as a precaution because of associations that the man is believed to have had". "Too many deaths [of Russian exiles] have been happening". His family has been informed and a post-mortem examination will be held in due course.
He later said he was told at the time that he would be killed on his way to court, saying: "I was told the way it would happen".
In the 1990s, Glushkov worked for the state airline, Aeroflot, along with Berezovsky's LogoVaz auto company.
In March 2013, Berezovsky was found hanged in his ex-wife's home.
Glushkov came to the United Kingdom after being freed from prison and spoke out against Berezovsky's death claiming he never believed his friend died of natural causes. An inquest recorded an open verdict.
In 2017, during a trial in absentia in Russia, Glushkov was sentenced to eight years in prison for stealing $123m from Aeroflot.
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