14 March, 2018
Police said the death was not linked to the poisoning of Sergei Skripal and his daughter in Salisbury.
Russian oligarch who moved to Britain in the early 2000s, Berezovsky became a strident critic of Russian President Vladimir Putin, and was found dead on the bathroom floor at his home in southern England in March 2013.
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".
It said counter-terrorism detectives are leading the investigation "as a precaution because of associations that the man is believed to have had".
Nikolai Glushkov, 68, was reportedly found by his family and friends at his house in New Malden, London and they summoned an ambulance at 10:46pm.
He said: "I'm definite Boris was killed".
Glushkov once worked for various Berezovsky enterprises, including the flagship Russian airline Aeroflot and the LogoVAZ auto company.
A post-mortem examination will be held in due course and the death is now being treated as an unexplained, the police said.More news: Two dozen arrested in brawl ahead of Richard Spencer speech
Glushkov had a nasty fall-out with Putin, 65, in 1999 when he was jailed for money laundering and fraud.
'I have quite different information from what is being published in the media'.
In 2010, Glushkov received political asylum in the UK.
"Boris was strangled. Either he did it himself or with the help of someone".
There, he gave evidence in court against Roman Abramovich, another Russian oligarch who remains close to the Kremlin. Too many bodies are happening. Last year a Russian court found Glushkov guilty and sentenced him in absentia to eight years in prison, said the Guardian.
Neighbour Patricia Egan said Mr Glushkov had lived there for several years, describing him as well educated and "a lovely fellow".
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.
Russian Federation on Tuesday dismissed accusations of any involvement in the poisoning of the ex-spy and his daughter as "nonsense, " saying it will only cooperate with a British investigation if it receives samples of the nerve agent believed to have been used.