Investigative website Bellingcat issued these images of the second suspect in the novichok poisoning attack of Sergei and Yulia Skripal

The second Russian man accused of launching the Salisbury novichok attack was also a decorated "hero of the Russian Federation", investigators have said.

Experts from the website Bellingcat said a photograph showed the man shaking hands with Vladimir Putin as he received the country's highest award.

They have named the alleged assassin who arrived in the UK under the alias Alexander Petrov as Dr Alexander Yevgenyevich Mishkin, who was employed by Russia's GRU intelligence agency.

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The 39-year-old graduated from one of Russia's elite Military Medical Academies, the group's website said.

During his studies he was recruited by the GRU 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, it added.

Bellingcat has already identified the assassin who arrived in Britain under the name Ruslan Boshirov as Colonel Anatoliy Chepiga - a highly decorated officer who also worked for the GRU.

A spokesperson for the Home Office said: “We are not commenting as this is still a police investigation.”

The men are believed to have smeared novichok on Sergei Skripal's front door on 4 March and returned to Moscow hours later.

The attack left Mr Skripal and his daughter Yulia critically ill, while Dawn Sturgess, 44, was later accidentally exposed to the same nerve agent and died in July.

Theresa May said their actions were not a “rogue operation” and would have been approved at a senior level in Moscow.

Police release images of suspects in connection with Salisbury attack Show all 19 1 /19 Police release images of suspects in connection with Salisbury attack Police release images of suspects in connection with Salisbury attack CCTV – Salisbury train station The two suspects charged in relation to the attack on Sergei and Yulia Skripal at Salisbury train station at 16:11hrs on 03 March 2018 Metropolitan Police Police release images of suspects in connection with Salisbury attack Suspects Suspects Ruslan Boshirov and Alexander Petrov, Russian nationals, approximately 40 years old, who travelled on a Russian passport. It is likely that they were travelling under aliases and that these are not their real names Metropolitan Police Police release images of suspects in connection with Salisbury attack Evidence Bottle and applicator recovered by police from Charlie Rowley’s address in Muggleton Road Metropolitan Police Police release images of suspects in connection with Salisbury attack Evidence A counterfeit perfume box that was discovered by nerve agent victim Charlie Rowley, who later gave it, and the bottle inside, to his girlfriend Dawn Sturgess Metropolitan Police/AFP/Getty Police release images of suspects in connection with Salisbury attack Rowley has previously said he felt lucky to be alive after giving a perfume bottle that contained the nerve agent Novichok to his girlfriend Dawn Sturgess, who later died Metropolitan Police/AFP/Getty Police release images of suspects in connection with Salisbury attack Suspeccts The CPS has issued European Arrest Warrants for the extradition of 'Boshirov' and 'Petrov' in connection with the Novichok poisoning attack on Sergei Skripal and his daughter Yulia in March Metropolitan Police/PA Police release images of suspects in connection with Salisbury attack CCTV – ‘Boshirov' at Gatwick airport Movements in detail - At 3pm on Friday, 2 March, the suspects arrived at Gatwick airport, having flown from Moscow on Aeroflot flight SU2588 Metropolitan Police Police release images of suspects in connection with Salisbury attack CCTV – ‘Petrov’ at Gatwick airport From the airport it is believed that they travelled by train into London, arriving at Victoria station at approximately 5.40pm Metropolitan Police Police release images of suspects in connection with Salisbury attack CCTV – Salisbury train station, 11:48hrs on 4 March 2018 They then travelled on London public transport to Waterloo station and were in the area between approximately 6pm and 7pm. They travelled to the City Stay Hotel in Bow Road, East London, where they stayed on Friday, 2 March, and Saturday, 3 March. On Saturday, 3 March, they left the hotel and took the underground to Waterloo station, arriving at approximately 11.45am, where they caught a train to Salisbury, arriving at approximately 2.25pm Metropolitan Police Police release images of suspects in connection with Salisbury attack City Stay Hotel in Bow Road Police officers stand outside the City Stay Hotel in Bow where on Sunday, 4 March, 'Boshirov' and 'Petrov' made the same journey from the hotel as they did the previous day, again using the underground from Bow to Waterloo station at approximately 8.05am, before continuing their journey by train to Salisbury Getty Police release images of suspects in connection with Salisbury attack CCTV – Wilton Road, Salisbury, 11:58hrs on 4 March 2018 CCTV shows them in the vicinity of Mr Skripal’s house and we believe that they contaminated the front door with Novichok Metropolitan Police Police release images of suspects in connection with Salisbury attack CCTV – Fisherton Road CCTV image of both suspects on Fisherton Road, Salisbury at 13:05hrs on 4 March, 2018 Metropolitan Police Police release images of suspects in connection with Salisbury attack CCTV – Salisbury train station, 13:50hrs on 4 March 2018 They left Salisbury and returned to Waterloo Station, arriving at approximately 4.45pm and boarded the London Underground at approximately 6.30pm to London Heathrow Airport Metropolitan Police Police release images of suspects in connection with Salisbury attack CCTV – Heathrow airport security, 19:28hrs on 4 March 2018 From Heathrow Airport, they returned to Moscow on Aeroflot flight SU2585, departing at 10.30pm Metropolitan Police/PA Police release images of suspects in connection with Salisbury attack Scene investigations The police investigation was carried out over 6 months. Ex-Russian spy Sergei Skripal and his daughter Yulia were found on March 4 in a critical condition on a bench outside the Maltings shopping centre in Salisbury AFP Police release images of suspects in connection with Salisbury attack Victims Former Russian spy Sergei Skripal, right, and his daughter Yulia Rex Police release images of suspects in connection with Salisbury attack Victims Detective Sergeant Nick Bailey who rushed to the aid of the Skripals was also taken to hospital in a serious condition after falling ill when attempting to help them PA Police release images of suspects in connection with Salisbury attack Victims Dawn Sturgess, a 44-year-old mother of three, died after falling ill when partner Charlie Rowley gave her a perfume bottle that contained the nerve agent Novichok Facebook/AFP/Getty Police release images of suspects in connection with Salisbury attack Scene investigations The home of Charlie Rowley in Muggleton Road, Amesbury, where he and Dawn Sturgess were exposed to the deadly nerve agent Novichok PA

The activities of the GRU have come under further scrutiny after the agency was accused of trying to hack the global chemical weapons watchdog as it worked to identify the substance used.

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 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.