Berezovsky subsequently fell out with Yeltsin's successor, President Vladimir Putin, and Glushkov found himself caught up in a politically charged corruption case.
Glushkov was best-known for being a close associate of Boris Berezovsky, a Russian oligarch who fled to Britain in the early 2000s after falling out out with Putin. An inquest failed to establish if he had committed suicide or died from foul play.
But it said there was "no evidence to suggest a link to the incident in Salisbury", adding that the death was being treated as "unexplained".
According to the Russian Embassy in London, the United Kingdom refused to extradite Glushkov in February 2016 on charges of large-scale fraud and embezzlement during his time as the deputy director of the Russian national airline Aeroflot. Glushkov was subsequently accused of fraud, larceny and money laundering overseas. He was sentenced to three years and three months in prison.
In 2010, he fled to the United Kingdom, where he was granted political asylum.
Mr Glushkov gave evidence in the high profile court battle between Berezovsky and Chelsea owner Roman Abramovich in 2011.
Glushkov was a Russian businessman who worked closely with Berezovsky in 1990s.
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According to the RBK Russian news site, Glushkov was found guilty of abuse of power in a financial scandal at Aeroflot, and was convicted in absentia of fraud previous year for allegedly stealing more than $100 million from the company.
The Metropolitan Police said an investigation is underway, but did not name Mr Glushkov.
News of Glushkov's death comes amid heightened tensions between the London and Moscow over the recent poisoning of a former Russian agent and his daughter.
In 2013, Berezovsky was found dead in his home in the United Kingdom, apparently after committing suicide.
"It is extremely worrying that chemical agents are still being used to harm people".
The regulator said Tuesday that it has a duty "to be satisfied that broadcast licensees remain fit and proper to hold their licenses".
The Russian Foreign Ministry, meanwhile, says it has handed the British ambassador a note of protest regarding the accusations, calling them "baseless", "provocative" and "another unscrupulous attempt of the British authorities to discredit Russia".