Evidence suggests the former spy was active across Europe, perhaps even investigating the Russian mafia.
Russian spy poisoning
A tiny Russian village has been revealed as Salisbury suspect's former home.
The second suspect in the Salisbury nerve agent attack was also a highly decorated officer in Russian military intelligence, it has been claimed.
At a news conference in the Houses of Parliament on Tuesday, Cristo Grozev, an investigator for the Bellingcat website said Mishkin had received the award of Hero of the Russian Federation from President Vladimir Putin.
Mr Grozev said the reporters from the Russian website The Insider had managed to reach Mishkin's home village of Loyga, where they spoke to seven people who confirmed his identity.
"They confirmed that their homeboy Alexander Mishkin was the person who moved on to military school and then became a famous military doctor and who received the award of Hero of the Russian Federation personally from President Putin," he said.
"His grandmother, with whom he grew up who happens to be a medical professional, has a photograph, in her own words, that has been seen by everybody in the village, of President Putin shaking Mishkin's hand and giving him the award."