One of the suspects in the Skripal poisoning case is a military doctor, it has been claimed.
Dr Alexander Mishkin has been identified by an online investigative group as one of the two men who carried out the deadly Salisbury nerve agent attack.
It comes a week after his alleged accomplice was named as Colonel Anatoliy Chepiga – said to be a senior officer in the Russian military intelligence service.
Here is what we know so far:
On September 5, the Prime Minister told MPs that two Russian nationals were suspected of travelling to the UK to murder former spy Sergei Skripal with the nerve agent Novichok.
The man believed to be Mishkin used the alias Alexander Petrov, while Chepiga used the name Ruslan Boshirov.
CCTV images tracked their movements from arriving in the UK on March 2 until their return to Russia late on March 4, the day of the attack.
Evidence gathered by intelligence agencies led the Government to conclude the men were officers from the Russian military intelligence service, also known as the GRU.
– Putin’s denial
A week later, Russian president Vladimir Putin publicly denied the men identified by the UK were responsible.
He said there was “nothing criminal” about the men and said they were civilians. Mr Putin made a surprise appeal for Petrov and Boshirov to appear in public to dispel doubt about their true identity.
– The interview
On September 13, the men appeared on Russian state-funded news channel RT.
In a bizarre interview Boshirov said they travelled to the “wonderful” Wiltshire city to see Stonehenge and Old Sarum after recommendations from friends.
He told the interviewer he wanted to see the world-renowned Salisbury Cathedral, which is “famous for its 123m spire” and historic clock.
Boshirov acknowledged they may have been near Mr Skripal’s house but said they did not know where it was. He said his life had been turned “upside down” after he was named as a suspect.
– Bellingcat revelations
On October 8 investigative group Bellingcat reported Alexander Petrov’s true identity as Dr Alexander Yevgenyevich Mishkin – a highly trained military doctor with the GRU.
The 39-year-old was allegedly born in a village Archangelsk District in the north of European Russia and graduated from one of Russia’s elite military academies.
He is said to have trained specifically for a life as a naval doctor and was allegedly recruited to the GRU during his medical studies and assumed his undercover identity in 2010.
Mishkin is said to have travelled extensively under his new identity, including making multiple trips to Ukraine.
On September 27, Bellingcat reported that Boshirov’s real name is Anatoliy Chepiga, a 39-year-old married father-of-one.
He is thought to be a highly-decorated colonel in the GRU, the group says.
Born in Amur Oblast in far-east Russia, he joined an elite military academy at 18.
The group said he graduated with honours and was assigned to a unit under GRU command.
The unit played a key role in the second Chechen War and he was deployed to the country three times, Bellingcat said. According to the group he was given his pseudonym at some point between 2003 and 2010.
– The president’s man?
The group said Col Chepiga was given the Kremlin’s highest state award, Hero of the Russian Federation, in secret in 2014.
The awards are usually handed out by Mr Putin himself, meaning it is “highly likely” the president would have been familiar with Col Chepiga’s identity.
What he was given the award for remains a mystery. In 2014 there were no military activities in Chechnya and Russia had not engaged in Syria.
The only region where Russia is alleged to have been involved was Eastern Ukraine, where any mission would have been classified.
Miushkin’s current military rank is unknown – but based on the fact he graduated from a military medical academy, he would at least be a senior lieutenant.
But 15 years have passed since he graduated, and Bellingcat believes he must now be either a lieutenant colonel or a full colonel.
– What has Russia said?
A spokeswoman for the Russian Foreign Ministry has previously dismissed Bellingcat’s claims, and said they were part of an “information campaign” to distract from the investigation into what really happened in Salisbury.
– What has the UK Government said?
The Home Office said it could not comment on the revelations as it is still a police investigation.
A spokesman for the Met Police, which is leading the investigation, said the force would not comment on speculation regarding the attackers’ identities.
Bellingcat says it has assessed data from the Russian central passport database.
The issue numbers on passports used by the men to travel to Britain differed by only three digits, making it “implausible” that they were issued through regular channels, the group said.