An inquest into the death of Russian tycoon Boris Berezovsky in the bathroom of his Berkshire mansion is about to begin in Windsor.

Although the post-mortem report said that Berezovsky's death was "consistent with hanging", the inquest will try to determine how exactly he died.

Detective Kevin Brown of Thames Valley police said initial reports ruled out "third-party involvement" in the 67-year-old oligarch's death.

But Berezovksy's friends sense foul play with one of them saying that it was not a case of suicide. Andrei Sidelnikov said: "If he really hanged himself why wasn't that known from the very beginning? I don't believe it was a suicide."

The BBC reported that some of the oligarch's close aides felt depression drove him to suicide following a humiliating verdict delivered by a London judge, who called Beresovsky an "unimpressive and unreliable witness" after losing a $6bn court case against Chelsea owner Roman Abramovich.

The real reason behind Berezovksy's death is expected to come out after further nuclear and chemical tests, which are likely to take a few weeks.

The judicial inquiry due to open is likely to be adjourneduntil all the test results are in.

Berezovsky, who was popularly called the "godfather of the Kremlin" in Russia, was granted political asylum in the UK in 2003 following a well-publicised feud with Russian President Vladimir Putin.

He survived a number of assassination attempts, including a bomb which exploded in his car in 1994, decapitating his driver in the process.