Toxicology may be key in supergrass death

Toxicology tests have been ordered by police investigating the sudden death of Russian supergrass Alexander Perepilichnyy, a wealthy businessman who collapsed outside his luxury Surrey mansion two weeks ago.

The revelation came as the Conservative MP who campaigned for sanctions against Russian officials implicated in the death of Sergei Magnitsky, right – another whistleblower linked to Mr Perepilichnyy – called on the Home Secretary to ensure every step was taken to uncover whether "foul play" might have been involved.

Mr Perepilichnyy, 44, was pronounced dead on 10 November outside his home in St George's Hill, a private estate on the outskirts of Weybridge. i revealed yesterday that the Russian businessman was helping Swiss investigators uncover a series of accounts used by Moscow tax officials who became exceedingly wealthy following a massive tax fraud. Alongside Mr Magnitsky, who originally exposed the fraud in 2008, Mr Perepilichnyy is the fourth person linked to the case to have died in mysterious circumstances.

Although it is possible he might have died from natural causes, there is intense pressure on Surrey Police and the coroners to ensure a full investigation is carried out, given the role Mr Perepilichnyy played in helping Swiss prosecutors and the growing concern over the murder of Russians on British soil. Investigators will hope that further testing on Mr Perepilichnyy's body will help them understand exactly how he died after the first post-mortem proved inconclusive.

Dominic Raab, a Tory MP who has campaigned for stricter sanctions against any Russians implicated in the Magnitsky case, called on Theresa May yesterday to provide "every technical support and all the national level resources required to conduct the most accurate and effective toxicology assessments possible".

i understands that Hermitage Capital Management, the British investment fund which hired Mr Magnitsky to uncover the $233m fraud carried out against them by a network of corrupt Russian Interior Ministry officials and underworld figures, wrote to Surrey Police on 17 November informing them of Mr Perepilichnyy's significance as a witness. But toxicology tests were not ordered until the last few days.

Hermitage last night would not comment on the reports. A Russian Interior Ministry official told the Interfax news agency: "Alexander Perepilichnyy does not have any relation to the so-called Magnitsky tax affair."