Video report by ITV News Security Editor Rohit Kachroo
Two men named as suspects in the Salisbury nerve agent attack are officers from the Russian military intelligence service, also known as the GRU, Prime Minister Theresa May has said.
Mrs May told MPs in the Commons how evidence obtained by security and intelligence agencies established the poisoning "was not a rogue operation" and was "almost certainly also approved outside the GRU at a senior level of the Russian state".
Scotland Yard and the Crown Prosecution Service earlier announced there is sufficient evidence to charge Russian nationals, Alexander Petrov and Ruslan Boshirov, with offences including conspiracy to murder.
Charlie Rowley, who also suffered Novichok poisoning in nearby Amesbury while his partner Dawn Sturgess died, has told ITV News he does not recognise suspects “but wants to see them brought to justice”.
Video report by ITV News Correspondent Rupert Evelyn
The CPS said it will not be applying to Russia for the extradition of the two men, but a European Arrest Warrant has been obtained and there is a "realistic prospect of conviction".
The offences include conspiring to murder Sergei Skripal and attempting to murder the ex-Russian spy, his daughter Yulia and Wiltshire Police detective sergeant Nick Bailey.
What we know about the suspects
While the suspects have been named as Alexander Petrov and Ruslan Boshirov, Assistant Commissioner of the Metropolitan Police Neil Basu said it is likely they were travelling under fake aliases.
The pair, believed to be aged around 40, are thought to be officers for the Russian military intelligence service, also known as the GRU.
The GRU is a highly disciplined organisation with a well-established chain of command, considered a threat to British citizens and allies..
The Prime Minister claimed the GRU was ordered by a member of the Russian state to send officers to the UK to carry out the attack.
The two suspects spent two days in the UK before arriving back in Moscow
Suspect's movements up to and following poisoning
At 3pm on Friday, March 2, the suspects arrive at Gatwick airport, having flown from Moscow on Aeroflot flight SU2588, two days before the attack.
They then travel by train into London, arriving at Victoria station at approximately 5.40pm.
They travel on London public transport to Waterloo station the travel to the City Stay Hotel in Bow Road, East London, where they stayed on Friday, 2 March, and Saturday, March 3.
On Saturday, March 3, they leave the hotel and take the underground to Waterloo station, where they caught a train to Salisbury, arriving at approximately 2.25pm. It is believed this trip was for reconnaissance of the Salisbury area there was no risk to the public from their movements on this day.
They take the same route when they return to London on the afternoon of Saturday, March 3. Leaving Salisbury at approximately 4.10pm and arriving in Bow at approximately 8.05 pm.
On Sunday, March 4, they make the same journey from the hotel, again using the underground from Bow to Waterloo station at approximately 8.05am, before continuing their journey by train to Salisbury.
CCTV shows them in the vicinity of Mr Skripal’s house and it is believed they contaminated the front door with Novichok.
They leave Salisbury and return to Waterloo Station, arriving at approximately 4.45pm and board the London Underground at approximately 6.30pm to London Heathrow Airport.
From Heathrow Airport, they return to Moscow on Aeroflot flight SU2585, departing at 10.30pm on Sunday, March 4.
Police say there is no evidence that they re-entered the UK after that date and it is not thought the Amesbury poisonings were intentional.
Mr Basu said: "We do not believe Dawn and Charlie were deliberately targeted, but became victims as a result of the recklessness in which such a toxic nerve agent was disposed of.
"We know that Novichok was applied to the Skripals' front door in an area that is accessible to the public, which also endangered the lives of members of the public and emergency service responders."
The announcement comes after the Organisation for the Prohibition of Chemical Weapons (OPCW) confirmed the toxic chemical that killed Ms Sturgess in Amesbury and left Mr Rowley fighting for his life was the same nerve agent as that which poisoned Sergei and Yulia Skripal.
Mr Rowley, a victim of the Amesbury poisoning, told ITV News: “I don’t recognise the two suspects, but I want to see them brought to justice.”
Speaking from his hospital bed on Wednesday, he said: “I am glad that police are making progress with their investigation but at the same time, it’s upsetting to see Dawn’s face everywhere, because it brings all the hurt and pain at losing her back to reality.
“It is progress to see the suspects identified in the Skripal case. But we need to make sure that these people are also held accountable for Dawn’s murder.
“She was a beautiful woman whose life was unjustly taken away because of them.”
Police reveal more detail on 'Novichok perfume bottle'
Mr Rowley told police he found a box he thought contained perfume in a charity bin on Wednesday, June 27.
Inside the box was a bottle and applicator which he attempted to put together and in doing so, spilled some of the contents on himself.
He said Ms Sturgess then applied some of the substance to her wrists before feeling unwell.
During a search of Mr Rowley's home address on July 10 a small box labelled as Nina Ricci Premier Jour perfume was recovered from a rubbish bag in the kitchen.
On July 11 a small glass bottle with a modified nozzle was found on a kitchen worktop. Tests established the bottle contained a significant amount of Novichok.
Police have spoken to perfume producer Nina Ricci and undertaken further inquiries, confirming that it is not a genuine Nina Ricci perfume bottle, box or nozzle.
Mr Basu added: "I’d like to reassure anyone who has bought Nina Ricci perfume from a legitimate source that they should not be concerned. It is safe."
What will happen now?
Mrs May says the Government "must now step up" collective efforts specifically against the GRU, who are considered a threat to British citizens and allies.
She added: "We are increasing our understanding of what the GRU is doing in our countries, shining a light on their activities, exposing their methods and sharing them with our allies, just as we have done with Salisbury.
"Together with our allies we will deploy the full range of tools from across our national security apparatus in order to counter the threat posed by the GRU."
Mrs May told MPs that the CPS did not have a policy of requesting extradition from nations who had constitutions barring the possibility.
She added: "If these two individuals step outside Russia then we will take every step possible to ensure that they are detained and brought to face justice here."
In response to calls for a stepping up of sanctions, she said: "We will indeed be stepping up our activity across the broad range of our capabilities and what is available to us across our national security apparatus."
When asked by Tory MP Sir Desmond Swayne whether "a decision outside the GRU by the Russian State at a senior level" means Putin, Mrs May declined to confirm or deny.
She says: "I mean...a decision outside the GRU at a senior level in the Russian state."
The response from elsewhere in the UK
Labour leader Jeremy Corbyn said: "We will back any further reasonable and effective actions, whether against Russia as a state or the GRU as an organisation.
"I would encourage the Prime Minister to seek the widest possible European and international consensus for this to maximise its impact."
He added that "we utterly condemn the appalling attacks" and "commend the police and security services for their diligence in investigating this appalling crime".
Former foreign secretary Boris Johnson attacked Mr Corbyn's response to the developments.
He said: "I think the whole House will have noted what I'm afraid was the somewhat weaselly language of the leader of the Opposition in failing to condemn what is now, I think, incontrovertible, in the eyes of all right-thinking people, involvement of the Russian state at the highest level in the Salisbury poisonings."
Sue Hemming, CPS director of legal services, said: "Prosecutors from CPS Counter Terrorism Division have considered the evidence and have concluded there is sufficient evidence to provide a realistic prospect of conviction and it is clearly in the public interest to charge Alexander Petrov and Ruslan Boshirov, who are Russian nationals."
She added: "A realistic prospect of conviction means the CPS is satisfied on an objective assessment that the evidence can be used in court and that an objective, impartial and reasonable jury hearing the case, properly directed and acting in accordance with the law, is more likely than not to convict these two individuals of the charges."
Britain's most senior officer, Metropolitan Police Commissioner Cressida Dick said: "We remain absolutely determined to identify and bring about a prosecution in the UK courts of those persons responsible for these attacks and we will do all we can to get justice for the victims and their families."
How have the Russians reacted?
Russian Foreign Ministry spokeswoman Maria Zakharova said the names and images of the suspects released by Britain "say nothing to us."
Ms Zakharova called on Britain to cooperate with Russian law enforcement agencies on the investigation.
She also criticised London for turning down Moscow's request to see the case files.
Around the time police announced suspects, a bizarre tweet appeared on the twitter account of the Ministry of Foreign Affairs of Russia, criticising Theresa May's dance moves.
What happened in Salisbury and Amesbury?
Former Russian double agent Sergei 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 along with Detective Sergeant Nick Bailey but all three were discharged.
Three months after the Skripals poisoning Dawn Sturgess and her partner Charlie Rowley fell ill at his home in Amesbury, near Salisbury, on June 30.
The former, a mother of three, died in hospital eight days later having never regained consciousness.
They were exposed to the military grade nerve agent from a perfume bottle discarded by those responsible for the attack on Mr Skripal and his daughter.
The incident sparked international outrage and resulted in the mass expulsion of Russian diplomats from several countries worldwide.
More than 117 agents were ordered to leave various countries in what Theresa May called the "largest collective expulsion of Russian intelligence officers in history".
In a tit-for-tat response, Moscow expelled dozens of UK and US diplomats, bringing tensions between Russia and the West to a post-Cold War all-time high.