Metropolitan Police confirmed a man in his 60s was found at a home in Clarence Avenue, New Malden, on Monday and that the cause of his death is unexplained.
"The death is now being treated as an unexplained", said London police."There is no evidence to suggest a link to the incident in Salisbury".
Berezovsky, a powerful oligarch and one-time supporter of Putin who turned against his former protege, was found hanged in a bathroom at his home outside London in 2013.
At the time of his death, he was living alone in New Malden, south-west London and was said to be a "nice man" who used to give his neighbour's children gifts at Christmas.
A post-mortem is due to take place in the coming days.
Police were quick to suggest there is now no evidence to link the death to events in Salisbury, where the former spy Sergei Skripal and his daughter Yulia were poisoned with a weapons-grade nerve agent that was only ever produced in Russian Federation.
He was a close associate of Russian oligarch Boris Berezovsky, who was a friend of murdered spy Alexander Litvinenko.
London police said its Counter Terrorism Command is leading the investigation "as a precaution because of associations that the man is believed to have had".
In 2000, he was arrested in connection with the embezzlement of Aeroflot's funds, and later charged with fraud and money laundering.
Glushkov, who has been an executive at state airline Aeroflot and also worked for Berezovsky's vehicle company LogoVAZ, followed and was granted asylum in 2010.
Britain granted Berezovsky political asylum three years later on the grounds his life would be in danger if he went back home.
"The death is now being treated as an unexplained". Natasha is believed to live in the UK.
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".