WHEN a Russian exile dies suddenly after providing explosive evidence to an anti-Kremlin activist, a degree of suspicion is natural. Now it seems justified. A toxicologist told a pre-inquest hearing on May 18th into the death of Alexander Perepilichnyy, an émigré Russian banker, that his stomach contained a compound associated with the poisonous plant gelsemium. The coroner adjourned the hearing until September, pending further tests.

The new evidence raises questions both about Mr Perepilichnyy’s death and the authorities’ investigation of it. When he collapsed and died on November 10th 2012, jogging near his Surrey mansion, the police saw no signs of foul play. Two inconclusive post-mortems and a “full and detailed range of toxicology tests” found “no suspicious circumstances”, police say.

But shortly before his death, Mr Perepilichnyy, a fit 44-year-old who was on a Russian gangland hit-list and had also been threatened with prosecution by the authorities in Moscow, had taken out a large life-insurance policy. Though lawyers will not comment, it is thought to be the insurers’ investigation which found the gelsemium traces.

This vindicates Bill Browder, an American-born financier who made a fortune in Russia and now campaigns against corruption from exile in London. Mr Perepilichnyy, who had deep experience in the murkiest corners of offshore finance, had greatly helped Mr Browder’s investigators trace money stolen in what they term a huge tax fraud by Russian officials. Mr Browder has lambasted the police for botching the case. He says they ignored the “French connection”: three unexplained days Mr Perepilichnyy spent in Paris just before his death. Oddly, he booked two hotels and spent €1,200 ($1,340 or £860 at today’s rates) at Prada. That purchase—presumably a gift—is unaccounted for; nor does anyone seem to know what he was doing, what he ate, and with whom.

The seeming official incuriosity is all the odder given the high death rate among prominent Russian exiles in Britain. In 2006 Alexander Litvinenko, a former Russian security official, was poisoned with polonium, a rare radioactive substance. He had been working with British intelligence on an investigation of links between senior Kremlin officials and Russian organised crime in Spain. British officials believe the Russian state was involved in his murder. In June 2007 a Russian oligarch, the late Boris Berezovsky, temporarily fled Britain citing an attempt on his life. A putative assassin was arrested and deported to Russia. (Mr Berezovsky, who had become a ferocious critic of Vladimir Putin’s regime, later died in an apparent suicide.) His business associate, the tycoon Arkady “Badri” Patarkatsishvili, died of a presumed heart attack in 2008.

Surrey Police declines to comment until after the inquest. There may be even more questions by then.