Security Editor Rohit Kachroo reports on the man suspected of being in charge of the team who carried out the Salisbury poisoning in 2018
A third Russian spy faces charges of attempted murder over the Salisbury Novichok poisonings in 2018.
Sergei Skripal and his daughter Yulia were left fighting for their lives in March 2018 when members of a Russian military intelligence squad are believed to have smeared the nerve agent Novichok on Mr Skripal’s door handle in Salisbury, Wiltshire.
Detective Sergeant Nick Bailey, the first person to enter Mr Skripal's home after the incident, also became seriously ill.
Denis Sergeev, who operated under the cover persona of Sergey Vyacheslavovich Fedotov, is believed to be a member of the Russian military intelligence service, the GRU and is the third man to be charged in connection with the incident.
He is thought to have arrived at Heathrow Airport at around 11am on March 2, 2018.
Fedotov arrived about four hours before the other two suspects - Alexander Petrov, 41, and Ruslan Boshirov, 43 - arrived at Gatwick Airport.
He stayed at a hotel in central London and met with Petrov and Boshirov more than once in the city. He left for Moscow on March 4 at around 1.45pm.
Global Security Editor Rohit Kachroo explains potential concerns over Russian influence in other countries
What happened in Salisbury and Amesbury in 2018?
Former Russian double agent Mr Skripal, 66, and his daughter Yulia, 33, were found unconscious from the effects of the military nerve agent Novichok on a bench in the cathedral city of Salisbury on March 4.
They were admitted to Salisbury District Hospital and both survived.
Detective Sergeant Bailey was also admitted to hospital.
Three months later, on June 30, Dawn Sturgess and her partner Charlie Rowley fell ill at his home in Amesbury, near Salisbury.
Ms Sturgess died in hospital eight days later having never regained consciousness.
They were exposed to the nerve agent from a perfume bottle discarded by those responsible for the attack on Mr Skripal and his daughter.
Tests were carried out in the hotel room Fedotov stayed in found no traces of Novichok, the nerve agent used to poison Mr Skripal and his daughter.
Police say there is evidence to suggest that Petrov, Boshirov and Fedotov previously worked together for the GRU in operations outside of Russia.
It is believed Ruslan Boshirov’s real name is actually Anatoliy Chepiga and Alexander Petrov’s is Alexander Mishkin.
All three suspects are thought to be in Russia and there are currently no extradition arrangements between the UK and Russia.
Mr Rowley, reacting to news of a third man facing charges, told ITV News he is "beginning to lose hope in justice."
Three years ago, Mr Rowley revealed to ITV News how the sealed box of perfume he gave to his girlfriend Ms Sturgess contained the deadly nerve agent.
He later fell critically ill himself. Ms Sturgess died eight days later.
He pointed to the fact that no progress has been made in the three years since - and that he sees no reason to believe anything will change.
'What difference is it going to make? None whatsoever': Charlie Rowley says the latest news has given him no fresh hope for justice
Deputy Assistant Commissioner Dean Haydon, who has been the investigation, said: This marks another significant development in our investigation.
"Ever since these terrible incidents occurred, we were clear that we would be relentless in our investigation and our pursuit of justice for the victims of the attacks and their families.
"While public attention gradually moved away from what happened in Salisbury and Amesbury, the investigation team has remained absolutely focused, meticulously poring over the evidence and building our case."
Mr Hayden continued to appeal to the public for information about the three suspects.
Fedotov has been charged with conspiracy to murder Mr Skripal; attempted murder of Mr Skripal, his daughter Yulia and Detective Sergeant Nick Bailey; causing grievous bodily harm with intent to Yulia Skripal and DS Bailey; and possession and use of a chemical weapon.
What is the significance of the latest development? ITV News Global Security Editor Rohit Rachroo writes:
A request for the extradition of the third Salisbury poisoning is almost certain to be met with a blunt rejection. It is written into the Russian constitution that its citizens may not be extradited to another state.
British authorities have been trying to put the other two suspects, ‘Boshirov’ and ’Petrov’, in a UK court for three years.
The Moscow government rejected that and put the men on state TV instead where they claimed they were in Salisbury for an innocent sightseeing trip to see the cathedral’s “123-metre spire”.
The name of the third suspect has been known by authorities for several years and was widely reported in the media.
Scotland Yard officers have been working with police in Bulgaria and Czech Republic, where the three men are suspected of being involved in plots.
Nick Price, CPS Head of Special Crime and Counter Terrorism Division, said "there is sufficient evidence to provide a realistic prospect of conviction".
He said the UK will not be applying to Russia for the extradition of Fedotov, as Russia does not permit the extradition of its own nationals.
He said: "Russia has made this clear following requests for extradition in other cases. Should this position change then an extradition request would be made."
Speaking in the Commons on Tuesday, Home Secretary Priti Patel said the "appalling" poisonings shook the entire country and "united our allies in condemnation".
She went on: "This is an ongoing investigation and so we are limited in terms of what can be said about these three individuals.
Ms Patel added: "This House has profound differences with Russia, by annexing Crimea in 2014, igniting the flames of conflict in eastern Ukraine and threating western democracies, including by interfering in their elections, Russia has challenged the fundamental basis of international order.
"Although attacks like this are uncommon, it is not the first time Russia has committed a brazen attack in the UK."
But Downing Street has already acknowledged it would be "futile" to seek to bring Fedotov to justice while he remained in Russia.
A No 10 spokesman said: "We don’t have an extradition treaty with Russia and, as we have found with other cases such as that of Litvinenko, any formal extradition request is futile."
Former prime minister Theresa May, who was in No 10 at the time of the Salisbury attack, called for the government to do "all it can" to bring the suspected attackers to justice.
"The use of a chemical weapon – Novichok – on the streets of Salisbury was an appalling crime which sadly led to the death of an innocent British woman, Dawn Sturgess," she said.
"I congratulate the police and all those involved in identifying this third individual and in developing the evidence leading to charges against him.
"This is further confirmation that responsibility for this attack lies firmly in the hands of the Russian state.
"I urge the UK government to do all it can to bring the individuals concerned to justice."
Detectives still want to hear from anyone who may have seen the fake ‘Nina Ricci’ perfume box or bottle before it ended up at Charlie Rowley’s address in July 2018.
Anyone who saw the pink box, or glass bottle between March 4 and June 27 should call police on 0800 789 321 or email firstname.lastname@example.org.
The poisoning in 2018 sparked international outrage and resulted in the mass expulsion of Russian diplomats from several countries worldwide.