During the final months of the former USSR, Mirzayanov told a Russian newspaper about the work he was conducting. Despite believing he was “doomed” to spend his time in jail, he felt as though he had to follow his conscience, reports The I newspaper.

However authorities were unable to prosecute Mirzayanov because the relevant legislation ceased to exist after the fall of the Soviet Union. There were attempts to put him through a “kangaroo court” in 1994 but Mirzayanov was able to move to the United States.

He however remained concerned that Novichok had not been destroyed during the USSR’s collapse. In 2008 he published a book exposing the nerve agent, including the relevant chemical formulas used to create weapons.

Eight days later he was stunned when former Russian military officer Sergei Skripal and his daughter Yulia were poisoned with Novichok in Salisbury, Wiltshire. The-then Prime Minister Theresa May announced the weapon was “part of a group of nerve agents known as Novichok”.

Mirzayanov was not just “shocked” to hear the word Novichok, but says he never expected it to be used as an assassination method. Russia had denied any involvement with the attack, which resulted in the death of 44-year-old Brit Dawn Sturgess, but an inquiry found Putin was likely to have authorised the assasination attempt.

It also criticised the fact Sergei Skripal was not given a new identity when he moved to the United Kingdom. However experts felt it was “very clear” that Skripal “wanted to live in the open and didn’t want to hide in the shadows”.

Mirzayanov believes the agents who sprayed Novichok on the Skripals’ door handles were “in a rush” meaning they didn’t coat it enough to kill them. He also suspects that Alexei Navalny, the Russian opposition leader, was not poisoned with Novichok in 2020.

He told The I: “I guess they used new poison agent to kill Navalny. Not Novichok, because they don’t want scandals connected to this violation of chemical weapons conventions.”

Mirzayanov fears Putin is “still developing” new varieties of chemical weapons that will be even more difficult to counter and trace. Much of Mirzayanov’s work at Foliant, a clandestine programme, was aimed at circumventing global bans on certain chemical weapons.

He explained: “Those chemical weapons are only weapons of mass destruction against civilians, innocent people.”

His own work in Russia means he urges United States President Donald Trump not to be “naive” when discussing any potential peace deals to end conflict in Ukraine. He claims that in every deal Russia signs, “they’re creating at least one loophole [to] circumvent this agreement”.