This year, the talk has been of a poisoned door handle. Back in August 1995, the focus fell on the mouthpiece of a white telephone.

According to court documents, it was from an office phone that banker Ivan Kivelidi and his secretary, Zara Ismailova, received lethal doses of a military-grade poison. Within two days, both would be dead.

The gruesome murder is considered a forerunner to the Skripal affair – the only other occasion that a poison resembling novichok was suspected in foul play.

The banker’s murder was eventually pinned on an acquaintance named Vladimir Khutsishvili. According to prosecutors, only Mr Khutsishvili was in Kivelidi’s office during the hours the poison could have been applied. In their version, the poison, an organophosphate nerve agent, was procured on the black market from a scientist called Leonid Rink.

Professor Rink was a star of Soviet science. Born in Leningrad, he worked at the Scientific Research Institute for Organic Chemistry and Technology in the closed town of Shikhany, in the southern Saratov region. From 1985, he was a member of the secret team that developed novichok nerve agents. He continued the research up until the mid-1990s.

By the time of Kivelidi’s murder in 1995, Professor Rink was already well-known to law enforcement. A year earlier, he had been suspected and questioned over the sale of military-grade poison to Chechen gangsters.

When it came to court, Professor Rink was not the most consistent of witnesses. But by his third statement, the most comprehensive, he accepted he had sold a “poison designed for humans” to criminals – after, he says, being threatened with violence. In total, eight or nine ampoules of this military-grade poison left his secret labs. This was easily enough to kill several hundred, as Professor Rink himself accepted in court.

The substance he sold was “known to a small circle of people”, “a government secret” and “similar in toxicity to [nerve agent] VX”, the court documents revealed.

The name of the chemical was not mentioned in the documents, but many have since drawn a straight line between it, novichok and the Skripals. Boris Kuznetsov, who initially acted as a lawyer for Mr Khutsishvili before leaving the country, has even claimed the mass spectrometry and infrared spectroscopy reports included in case documents offered the most physical evidence of the existence of the novichok programme. He said he had passed the reports to British authorities last month.

But mystery still shrouds the affair – and earlier this week, Professor Rink added to the confusion by disowning his earlier court statements.

He had not sold military-grade nerve agents on the black market, he insisted in an interview given to independent Russian publication The Bell. Instead, he had “tricked” the criminals by giving them “rat poison” in a “controlled handover” under the watchful eye of the FSB, Russia’s security services. He claimed to know “nothing” of the substance that killed Kivelidi.

A number of obvious questions arose from Professor Rink’s new assertions. If indeed the substances were sold under the control of the security services, how was it that two people ended up dead? Did that not then mean that the security services somehow knew of, or played a role in the murder? And what does that mean for the poisoning in Salisbury?

The Independent has reached out to Professor Rink for comment but was told via an intermediary that he was not prepared to talk.

“Facts are facts,” Mr Kuznetsov told The Independent. “Kivelidi was killed with a military-grade poison and Rink, in court, said he said he sold that poison. A man has served eight years in prison for murder. How can you now start denying things?”

For Mr Kuznetsov, Professor Rink’s new testimony was an attempt to place distance between Russia and the poison: “If the substance in the Kivelidi spectrums matches the substance found in Salisbury, you can only make one conclusion: the same security agency was involved.”

Skripal attack aftermath – in pictures Show all 15 1 /15 Skripal attack aftermath – in pictures Skripal attack aftermath – in pictures Scene of attack Members of the emergency services in hazard suits fix the tent over the bench where Sergei and Yulia Skripal were found unconscious on a park bench in Salisbury in March 2018. Getty Skripal attack aftermath – in pictures Victim - Sergei Skripal The retired Russian colonel and former double agent for MI6 was in a critical condition in hospital for more than two months after being exposed to novichok in Salisbury. He was given refuge in the UK after being jailed in Moscow for treason. Mr Skripal came to Britain as part of a high-profile “spy swap” in 2010 in which four men were exchanged for ten Russian "sleeper agents" in the US. In this image he is speaking to his lawyer from behind bars in Moscow in 2006. AP Skripal attack aftermath – in pictures Victim - Yulia Skripal Yulia Skripal was struck down by a novichok poison alongside her father Sergei. Facebook Skripal attack aftermath – in pictures Scene of attack A police officer stands guard outside a branch of the Italian chain restaurant Zizzi where the pair dined at before falling ill. It was boarded off whilst investigators worked on the building and later found traces of the chemical weapon within it. AFP/Getty Skripal attack aftermath – in pictures Scene of attack Large areas of central Salisbury were cordoned off by police following the discovery of the Skripals. Traces of nerve agent were also found in The Mill pub. PA Skripal attack aftermath – in pictures Victim - Nick Bailey Detective Sergeant Nick Bailey, rushed to the aid of the Russian ex-spy and his daughter who were targeted with a nerve agent. He was hospitalized after aiding them and didn't leave until three weeks after the attack. Wiltshire Police/Rex Skripal attack aftermath – in pictures Police investigation - Skripal’s home Police believe they were poisoned at home, and detectives found the highest concentration of novichok on the front door of Mr Skripal’s house. Getty Skripal attack aftermath – in pictures Theresa May visits scene of attack Britain's Prime Minister Theresa May spokes with Wiltshire Police's Chief Constable Kier Pritchard near where the Skripal's were found. Britain expelled 23 Russian diplomats over the nerve agent poisoning and suspended high-level contacts, including for the World Cup on March 14. Theresa May told parliament that Russia had failed to respond to her demand for an explanation on how a Soviet-designed chemical, Novichok, was used in Salisbury. AFP/Getty Skripal attack aftermath – in pictures Skripal days before attack Sergei Skripal days before he was exposed to Novichok, that has left him fighting for life. ITV News Skripal attack aftermath – in pictures Police investigation - military involvement British soldiers were deployed soon after the attack to help a counter-terrorism investigation into the nerve agent attack. One of the places they were asked to help out with was Skripal's home and it's surrounding. They were asked to remove a vehicle connected to the agent attack in Salisbury, from a residential street in Gillingham. AFP/Getty Skripal attack aftermath – in pictures Police investigation Personnel in protective coveralls and breathing equipment cover an ambulance with a tarpaulin at the Salisbury District Hospital. AFP/Getty Skripal attack aftermath – in pictures Police investigation The investigation extended to the grave of Sergei Skripal's son Alexander in London Road cemetery. Getty Skripal attack aftermath – in pictures Police investigation The Counter Terrorism Policing Network requested assistance from the military to remove a number of vehicles and objects from Salisbury. EPA Skripal attack aftermath – in pictures Home Secretary visits scene of attack Home Secretary Amber Rudd visited the scene of the nerve agent attack at the Maltings shopping centre on 9 March. Getty Skripal attack aftermath – in pictures Yulia Skripal speaks for the first time Yulia Skripal, speaking for the first time, said she felt lucky to have survived the nerve agent attack in Salisbury which left her fighting for life. Ms Skripal said her life had been “turned upside down” by the assassination attempt. But the Russian national added she hoped to return to her homeland one day, despite the Kremlin being blamed for the attack. Reuters

But there is, in fact, little agreement on what the Kivelidi spectrum actually shows.

Vladimir Uglyov, one of the scientists connected with the novichok programme, has suggested the spectrum matches A-234, one of the secret novichok nerve agents. But other scientists surveyed by The Independent cast doubt on that assertion.

According to Vil Mirzayanov, the scientist who first revealed Russia’s chemical weapons programme to the world, the substance most closely resembles tabun, a nerve agent first developed in Germany.

“There’s no fluoride in those charts, that’s the giveaway,” he said. It was “possible” that the substance represented a newer analogue of the novichok class of nerve agents, he said. “Rink was researching new substances to take over from novichok compounds if those were banned. But the spectrum could also be a fake. We don’t, of course, know if this spectrum is showing the material obtained on the crime scene. This is Russia.”

Dan Kaszeta, a London-based chemical defence consultant, told The Independent that the case was yet to be proven. “The whole episode could easily have been a novichok. Or not. The Kivelidi case is shrouded in vague information of mixed value and credibility.”

What the affair does show, however, was that in the crippling poverty of the Russian 1990s, dangerous military-grade poisons did occasionally go walkabout. And it is not likely that Professor Rink was the only scientist unable to resist criminal forces. Mr Mirzayanov himself told The Independent that he was also approached by criminals looking to obtain chemical weapons.

“It’s the first time in telling anybody this, but yes, in 1994, once, I was offered a million rubles to synthesise a poison,” he said. “It was a very short conversation. I said no. Everyone makes their own choices. When I didn’t have money, I went out and sold jeans on the highway.”

Such revelations undermine British suggestions that the Kremlin was “overwhelmingly likely” the only Russian actor capable of implementing a chemical weapon attack using novichok in Salisbury. With the substance floating about on the black market, any number of criminal and near-state groups could potentially have that capacity.

Three experts surveyed by The Independent agreed novichok-type substances sold in the 1990s could retain lethal potency two decades years later.

But even if poison were successfully smuggled into the UK, there are other barriers to it being used in an attack. Its application would, for example, likely require making a suspension with oil, and the substance would be very volatile. This, at the very least, would suggest expert involvement.

“These suspensions are so dangerous that even the smallest mistake will result in tragedy,” says Mr Mirzayanov. “You’re bound to have a mistake if you have no experience. And it’s here that we’re clearly talking about a state or military level of expertise.”

Concurrently, poor handling would also affect the potency of any nerve agent.

“One of the biggest drawbacks of novichok is that it is hydrolysed immediately,” said Mr Mirzayanov. “In retrospect, only an idiot would choose to use it for a murder in England with its 100 per cent humidity.”