Sky News' home affairs correspondent, Mark White, said Mr Glushkov's home in New Malden, southwest London, was being treated as a crime scene.
One of Mr Glushkov's friends was late Russian oligarch Boris Berezovsky, who fled to London in 2000 following a row with Vladimir Putin.
Glushkov, who has been an executive at state airline Aeroflot and also worked for Berezovsky's auto company LogoVAZ, followed and was granted asylum in 2010. In the meantime, Glushkov was charged with money laundering and fraud, ending up behind bars for five years in Russian Federation.
He was released in 2004, before he was granted asylum to the UK.
Scientology Network set for TV launch
Ron Hubbard, Scientology has grown into a religious movement with outposts around the world and some very famous members . The move ends months of speculation after the organisation set up its own studio with Scientology Media Productions .
He gave evidence in a case in 2011 brought by Mr Beresovsky against Roman Abramovich, who he claimed had cheated him out of £3.2bn.
Glushkov told the London court he had effectively been taken hostage by Putin's administration, which wanted to pressure Berezovsky to sell his stake in the TV station ORT.
Andrei Borovkov told Russian media outlets on March 13 that his client, Nikolai Glushkov, has died, but said he was unaware of the time and circumstances. In 2017, a Moscow court reviewed his case and he was sentenced to eight years in prison in absentia for stealing as much as $123 million from Aeroflot in the 1990s. "[But] I don't believe it was suicide", Glushkov said.
Glushkov died at his London home aged 68, and his cause of death is yet to be confirmed.
Mr Berezovsky was himself found dead on a bathroom floor at his home in southern England in 2013 with a scarf around his neck.
Pioneering French designer Hubert de Givenchy dies at 91
Givenchy was one of the first big designers to use black models, and in 1986 used only black models for one collection. He went on to work with Robert Piguet and Lucien Lelong in 1946, and then for Elsa Schiaparelli between 1947 and 1951.
They were found in Salisbury, around two and a half hours from London.
"He sometimes came in our shop many years ago, by the triangle, but I don't remember what he looked like".
As the fallout from the Skripal poisoning continued, Britain's media regulator, Ofcom, announced that Kremlin-backed news channel RT could lose its license to broadcast in the UK.
The White House on Monday condemned the poisoning of the ex-Russian spy in the U.K."The use of a highly lethal nerve agent on U.K. soil is an outrage".
Russian Federation reportedly dismissed the British claims as a "circus show", a "provocation" and "nonsense".
Ken Dodd dead; British comedy veteran was 90
Television personality Claire Sweeney, a fellow Liverpudlian, shared some photos of the star's 90th birthday party on Twitter. Comedian John Bishop, who was born in Liverpool, wrote on Instagram: "True comedy legend".