The coroner examining the mysterious death of a wealthy Russian whistleblower has been urged not to "brush away" the possibility he was poisoned.

Alexander Perepilichnyy, 44, collapsed and died while jogging near his home in Weybridge during 2012.

Over the past year-and-a-half, Coroner Nicholas Hilliard QC has been examining whether the businessman was murdered with poison or died of natural causes.

The inquest has heard how the married father-of-two had appeared on a "hit list" in Moscow before his death.

He had taken out £3.5 million worth of life insurance and applied for another £5 million worth of policies amid concern to provide for his family, it has been said.

Around that time, Mr Perepilichnyy had been helping UK-based campaigner Bill Browder's Hermitage Capital Investment to expose a 230 million US dollar (£142 million in November 2012) money-laundering operation.

And, a month before his death, he had fought off a legal challenge by a debt recovery firm allegedly led by the prime suspect in the Alexander Litvinenko poison case, Dmitry Kovtun.

Extensive tests have failed to identify any poison in Mr Perepilichnyy's body, although experts could not categorically rule out a toxin or even Novichok, which was used in the Salisbury case.

Surrey Police has faced criticism over its handling of the investigation and during the inquest it emerged that the contents of Mr Perepilichnyy's computer was lost.

However, Detective Superintendent Ian Pollard, of Surrey Police, has insisted there were no signs of "third party involvement or foul play".

In a closing statement, Bob Moxon Browne QC, for Legal and General, objected to the proposition that poisoning could be ruled more unlikely than the rare sudden adult death syndrome (SADs).

He said "It is certainly not lawful to say poisoning is unlikely and therefore death by SADs is likely."

Mr Moxon Browne quoted Sherlock Holmes' maxim that "Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth".

But he said the Perepilichnyy case was still "bristling with unknowns".

He said: "We do not know what was in Mr Perepilichnyy's stomach when he died. We do not know for certain what he had for lunch. CCTV was never interrogated. We do not know what phone calls Mr Perepilichnyy made.

"There are lots and lots of parallels as far as uncertainties are concerned."

On the question of whether Mr Perepilichnyy died of an unascertained cardiac arrhythmia, the lawyer said: "You might decide that it is not at all probable that someone in perfect health never had any symptoms or carried any genetic markers for this disability.

“In all those circumstances statistically it is an extremely rare event."

He said it was "necessary to grapple with the circumstances of Mr Perepilichnyy's life" to determine his death.

That included his connection with the fraud against Hermitage which provided a motive to kill him.

He said: "It is not a fanciful proposal that people might come from Russia with a view to harm someone they saw as the enemy."

Henrietta Hill QC, for Hermitage, called for a full narrative verdict to conclude death was unascertained.

She highlighted "significant uncertainty" over tests for poisoning.

Ms Hill told the court there were "at least 10 poisons" that remain possible culprits, meaning it was not reasonable to exclude it as a cause of death.