Video report by ITV News Security Editor Rohit Kachroo
The second suspect in the Salisbury nerve agent attack has been named by an investigative website as Dr Alexander Yevgenyevich Mishkin.
Bellingcat claims that the man identified as Alexander Petrov is in fact Alexander Mishkin, a 39-year-old doctor who graduated from one of Russia's elite Military Medical Academies.
During his studies he was recruited by the GRU military intelligence agency and by 2010 had relocated to Moscow, where he received his undercover identity - including a second national ID and travel passport - under the alias Alexander Petrov, Bellingcat further adds.
It continues that President Putin honoured Mishkin with the Hero of the Russian Federation Award in 2014. Those familiar with Mishkin’s family told Bellingcat they believe Russia’s highest award was given for Mishkin’s activities “either in Crimea or in relation to [former Ukrainian president] Yanukovich”.
Bellingcat's identification process included multiple open sources, testimony from people familiar with the person, as well as copies of personally identifying documents, including a scanned copy of his passport.
On Tuesday, it published analysis from Professor Hassan Ugail, an expert in in simulated age progression, who confirmed Mishkin is Petrov.
The report says, "Prof. Ugail confirmed unequivocally that the two photographs belong to the same person, accounting for the 15-year difference between the two."
The website alleges that Mishkin was born in a village in the Arkhangelsk District in the north of European Russia.
Bellingcat says that between 2011 and 2018 he travelled extensively under his new identity, including making frequent trips to Ukraine, the last of which was reportedly in December 2013, just ahead of the 2014 Ukrainian revolution which led to Russia's annexation of Crimea.
For his cover identity, Mishkin used most of his own details, including his date of birth and first name, and the first names of his parents, the website adds.
It continues that until September 2014 his home address was registered as the Moscow headquarters of the GRU, but he then moved to an apartment shared with Chepiga.
Bellingcat is the same website which in September claimed that the suspect named as Ruslan Boshirov was in fact Anatoliy Chepiga, a highly decorated colonel in the GRU intelligence service.
Following the March attack on former Russian spy Sergei Skripal and his daughter Yulia, the UK accused Petrov and Boshirov of the attempted murder of the pair.
Britain also accused Russia of responding with "obfuscation and lies" after the prime suspects in the Novichok attack claimed they visited the UK as tourists.
Petrov and Boshirov told Russian state-funded news channel RT they travelled to the “wonderful” city in Wiltshire after recommendations from friends.
The pair claimed they have been left fearing for their lives after Britain pointed to their involvement.
However, Russia's President Vladimir Putin said the men had been discounted as members of his security network, and insisted they were civilians.
UK authorities believe the pair smeared the highly toxic chemical Novichok on a door handle at the Wiltshire home of former GRU officer Mr Skripal on March 4, leaving him and his daughter critically ill.
On June 30, in nearby Amesbury, Dawn Sturgess, 44, and her partner Charlie Rowley, 45, were exposed to the same nerve agent.
Ms Sturgess died in hospital in July, just over a week after the pair fell ill.
A police officer who visited the home of the Skripals shortly after the attack, Nick Bailey, was also left critically ill from exposure to the substance.
A spokesperson for the Home Office said they would not comment on the latest claims as a police investigation is underway, however, it is understood that the identity is not disputed by UK security services.
Meanwhile, Tory MP Bob Seely, a member of the Commons Foreign Affairs Committee with a long-standing interest in Russia, said: "It is appalling that a medical doctor appears to have been part of a team of GRU operatives that attempted to deliver a lethal poison to their target - and accidentally killed another person by mistake.
"Whilst this operation has been a botched embarrassment for the Kremlin from beginning to end, it's worth remembering that we may not know about the GRU's successful operations and therefore shouldn't judge the GRU alone by their failures.
"The Government has shown strong resolve thus far, but it is yet more evidence that the UK needs to develop a long-term plan to understand and expose Russian subversion, as well as identifying the steps needed to protect our democracy."
The activities of the GRU have come under further scrutiny after the agency was accused of trying to hack the global chemical weapons watchdog which is investigating the Salisbury attack.
Officials in the Netherlands, where the Organisation for the Prohibition of Chemical Weapons (OPCW) is based, said four Russians had been expelled after the alleged cyber strike.
British intelligence helped thwart the operation which was launched in April, a month after the Novichok poisoning.
The GRU has also been blamed for a string of cyber attacks targeting political institutions, businesses, media and sport.
The National Cyber Security Centre (NCSC) said a number of hackers known to have launched attacks have been linked to the GRU.
The NCSC associated four new attacks with the GRU, on top of previous strikes believed to have been conducted by Russian intelligence.
Among targets of the GRU attacks were the World Anti-Doping Agency (Wada), transport systems in Ukraine, and democratic elections, such as the 2016 US presidential race, according to the NCSC.
The centre said it was "almost certainly" the GRU behind a "BadRabbit" attack in October 2017 that caused disruption to the Kiev metro, Odessa airport and Russia's central bank.