An inquest into the death of a Russian businessman by suspected assassination due to go ahead today was postponed this morning at the last minute.

Alexander Perepilichnyy, 44, died after he was found seriously ill outside his Weybridge home in St George's Hill on November 10, 2012.

His death sparked allegations of a “reprisal killing” after it emerged he had helped Swiss authorities in a major corruption investigation relating to an alleged multi-million-dollar fraud.

He was then publicly named as the source that led to the Swiss criminal proceedings.

Suspicions of murder strengthened after it was revealed at a previous hearing that a rare Chinese plant toxin, gelsemium, had been found in his stomach.

His death, which happened shortly after he took a jog around the leafy St George’s Hill estate in Weybridge was originally thought to be non-suspicious after two post-mortem examinations, but an inquest was called to investigate.

Mr Perepilichnyy had moved to Britain three years before his death after an alleged falling out with a Moscow crime syndicate.

He had also testified against people linked to the 2009 death of anti-corruption lawyer Sergei Magnitsky. Mr Perepilichnyy was the fourth person linked to that case to have died in strange circumstances.

At previous pre-inquest reviews, it had also emerged that he had taken out ‘millions of pounds worth’ of life insurance after receiving death threats and was reportedly on a hit list.

Henrietta Hill QC, representing Hermitage Capital Management, said the information and documents received from Mr Perepilichnyy was “explosive”.

Surrey Police were also accused of a “cover-up” at a pre-inquest review last month by top QC Geoffrey Robertson, representing Hermitage Capital Management.

Mr Robertson, a barrister with a history in constitutional, human rights, criminal and international law, criticised the force after some 45 documents in the case were said to have been marked as immune from interested parties due to sensitivity concerns.

He told the court: “This is, sir, with respect, entirely unsatisfactory. There is a clear order here which must not just show all indices but there must be an undertaking to allow us to inspect the documents.

“There has been a cover-up and now we ask the police for full public interest. They’ve asked for tape recordings to be turned off in your office, that’s illegal.

“They’re asking for an unlawful procedure. When [police lawyer] Miss Ventham talks about sensitivity, that’s not good enough, there needs to be a basis for that.”

Charlotte Ventham, representing Surrey Police, hit back stating: “I can’t let it pass without comment that Surrey Police are guilty of some cover-up and illegal activity. Both of those serious allegations are firmly rebutted and refuted.

“I thought I’d made that clear, we will not be urging unlawful procedures on this court.”

The inquest has now been postponed to late March.

Got a story? Call the newsdesk on 020 8722 6313 or email rachel.dickerson@london.newsquest.co.uk