Russian spy: What we know so far
The attempted murder of a former Russian double agent and his daughter on British soil has led to accusations of Russian state involvement.
The British government is expelling 23 Russian diplomats after Moscow refused to explain how a nerve agent was used against former Russian spy Sergei Skripal, 66, and his 33-year-old daughter Yulia in Salisbury on Sunday 4 March.
Prime Minister Theresa May said the chemical used in the attack had been identified as being part of a group of nerve agents developed by Russia known as Novichok.
Russia responded to the UK sanctions by saying it would expel 23 British diplomats, as well as closing the British Council in Russia and the British Consulate in St Petersburg.
This is what we know so far.
Timeline of events
- Yulia Skripal flew into London's Heathrow Airport on a flight from Russia at about 14:40 GMT on 3 March
- On 4 March, at about 09:15 GMT, Mr Skripal's car was seen in Salisbury in the area of London Road, Churchill Way North and Wilton Road
- At 13:30 GMT his car was seen driving down Devizes Road, towards the town centre
- Mr Skripal and his daughter arrived at the Sainsbury's upper level car park at the Maltings shopping precinct at 13:40 GMT
- Police said the pair went to The Mill pub before going to Zizzi restaurant at 14:20 GMT, staying until 15:35 GMT
- At 16:15 GMT emergency services received the first report of an incident
- Police found the pair on a bench outside Zizzi in an "extremely serious condition"
- A police officer who fell ill after attending the incident - Det Sgt Nick Bailey - was treated in hospital but discharged on 22 March
- 48 people have been assessed in hospital in relation to the incident
- Only Mr Skripal and his daughter Yulia remain in hospital
- Investigators have identified 131 people who have potentially been in contact with the nerve agent. None has shown symptoms
The investigation so far
Police have been treating the case as attempted murder.
Traces of the nerve agent were found at the Mill and Zizzi, where the Skripals spent the afternoon.
Eyewitness Jamie Paine said he saw a woman on a bench frothing at the mouth and her eyes "were wide open but completely white".
A doctor, who was shopping with her husband in the city centre on Sunday, said Ms Skripal was "slumped in her seat, completely unconscious" and had lost control of her bodily functions.
Assistant Commissioner Mark Rowley, head of counter-terrorism operations, said the Skripals had been "targeted specifically".
Up to 500 people who visited the pub or the restaurant on Sunday or Monday were told to wash their clothes and possessions to avoid any contamination.
Prof Dame Sally Davies, the chief medical officer for England, stressed the risk of harm was "low" but there was some concern that prolonged exposure over weeks and months could cause health problems.
There are 250 specialist counter-terrorism officers involved in the investigation.
Metropolitan Police Assistant Commissioner Neil Basu said the "prime focus" of the investigation, which could take months, was how the poison was administered.
Police have appealed for any witnesses who saw the pair in Mr Skripal's red BMW - licence plate number HD09 WAO - on the morning of the attack.
Police believe the car may have been in the areas of London Road, Churchill Way North and Wilton Road at about 09:15 GMT. At about 13:30 GMT it was seen being driven down Devizes Road towards the centre of town.
A vehicle that is believed to have been used by Mr Skripal's friend to pick up Yulia from the airport on 3 March was removed from Durrington, Wiltshire, by the Army on 19 March.
Officers have taken statements from about 400 witnesses so far and are looking at more than 750 pieces of evidence and 4,000 hours of CCTV.
About 180 military personnel were deployed to help remove vehicles and objects which may have been contaminated.
Personnel from the Defence Chemical Biological Radiological and Nuclear Centre at Porton Down in Wiltshire identified the nerve agent.
Experts from the Organisation for the Prohibition of Chemical Weapons (OPCW) arrived in the UK on 19 March to test samples of the chemical.
The results are expected to take a "minimum of two weeks", the Foreign Office said.
What are Novichok agents?
The name Novichok means "newcomer" in Russian, and applies to a group of nerve agents developed by the Soviet Union in the 1970s and 1980s.
Novichok's existence was revealed by chemist Dr Vil Mirzayanov in the 1990s, via Russian media. He says the nerve agents were designed to escape detection by international inspectors.
Professor Gary Stephens, a pharmacology expert at the University of Reading says Novichok is "a more dangerous and sophisticated agent than sarin or VX and is harder to identify".
Novichok agents are liquids, although others are thought to exist in solid form and could be dispersed as an ultra-fine powder.
Some of the agents are also said to be "binary weapons", meaning the nerve agent is typically stored as two less toxic chemical ingredients that are easier to handle.
When these are mixed, they react to produce the active toxic agent which can cause convulsions, shortness of breath, profuse sweating and nausea.
How has the government responded?
The UK expelled 23 diplomats after Prime Minister Theresa May said Russia was "culpable" for the poisoning of Sergei Skripal and his daughter.
Mrs May said Russia had responded to the situation with "sarcasm, contempt and defiance" and not provided any credible reasons.
She added there would be a "full and robust" response beyond what had been done for the Litvinenko poisoning case.
She announced a series of sanctions including:
- The expulsion of 23 diplomats - who must be gone within a week
- Ministers and the Royal Family will not attend the Fifa World Cup in Russia later this year
- Russian state assets will be frozen if there is evidence they will be used as a weapon against UK nationals and residents
- Checks on private flights, customs and freight will be increased
- All planned high-level contacts between the UK and Russia will be suspended
- The retraction of the state invitation to Russian's Foreign Minister Sergei Lavrov
Mrs May added there were other measures ready to be deployed if the UK faces more "Russia provocation".
Foreign Secretary Boris Johnson said Russian President Vladimir Putin was "overwhelmingly likely" to have ordered the attack.
He also said the UK government had evidence Russia had been stockpiling the nerve agent used in the attack over the last 10 years and had investigated ways of delivering such weapons for assassination.
After Russia announced sanctions of its own, Mrs May said the government would consider its next steps "in the coming days, alongside our allies and partners".
France, Germany, the US and UK said in a joint statement Russian involvement was "the only plausible explanation".
The European Council issued a statement agreeing, after talks in Brussels with Mrs May, that it was "highly likely" Russia was responsible.
The EU has recalled its ambassador to Moscow "for consultations", and some EU states have not ruled out the possibility of expelling Russian diplomats.
Nato Secretary General Jens Stoltenberg said the "UK is not alone" and Russia has underestimated the "resolve and unity" of the UK's allies.
The UN Security Council held an emergency meeting at the UK's request, where British deputy ambassador Jonathan Allen said Russia had used "a weapon so horrific that it is banned in war".
What has Russia said?
Kremlin spokesman Dmitry Peskov said Russia was not worried by international expressions of support for the UK and challenged Britain to "provide some confirmation".
He said: "Sooner or later, the British will have to show some proof to those 'colleagues' who say they are with UK on this; sooner or later will have to stand up its accusations."
The Russian foreign ministry has called Mrs May's allegations "insane" and the Russian Embassy in Britain has described the order for diplomats to leave as "unacceptable, unjustified and short-sighted".
The Russian Ministry of Defence described UK Defence Secretary Gavin Williamson as a "vulgar old harpy" after he said Russia should "go away and shut up".
Russia also said Mr Johnson's accusations that Mr Putin was most likely behind the attack were "shocking and unforgivable".
In response to the UK's sanctions, Russia's foreign ministry announced it would:
- Expel 23 British diplomats - who have been given one week to leave Moscow
- Close the British Consulate in St Petersburg
- End the activities of the British Council, which promotes cultural ties between the UK and Russia and language learning
It said it was responding to "provocative actions" by Britain.
Russian foreign minister Sergei Lavrov said the UK was "playing politics" and not taking into account an international pact on chemical weapons.
He said if the UK sends Moscow a formal request for an explanation under the Chemical Weapons Convention, Russia will respond within the set 10-day time limit.
Russia has also requested to be given a sample of the nerve agent used.
Russian foreign ministry spokeswoman Maria Zakharova said the UK was one of the most likely sources of the nerve agent, along with the Czech Republic, Slovakia, Sweden or possibly the United States.
She said a large number of ex-Soviet scientists had gone to live in the West, "taking with them the technologies that they were working on".
Russia's EU ambassador, Vladimir Chizhov, also suggested a UK research laboratory in Wiltshire could be the source of the nerve agent.
Who are the victims?
Colonel Skripal is a retired Russian military intelligence officer who was convicted of passing the identities of Russian intelligence agents working undercover in Europe to the UK's Secret Intelligence Service, MI6.
He was jailed for 13 years by Russia in 2006.
In July 2010, he was one of four prisoners released by Moscow in exchange for 10 Russian spies arrested by the FBI. He was later flown to the UK.
According to BBC Newsnight's diplomatic editor Mark Urban, in recent years Mr Skripal gave lectures at military academies offering insights into Russia's foreign military intelligence agency, the GRU.
A friend from college, Vladimir Svyatski, described Mr Skripal as "very active, with a positive attitude and creative".
A former colleague, Oleg Ivanov, told the BBC he was "the life and soul of party".
His daughter, Yulia, would regularly travel to the UK from her home in Moscow to visit her father, relatives told the BBC.
"She told me she liked everything [in the UK]," childhood friend Irina Petrova said. "They had an amazing place, and amazing house."
She had an "excellent" relationship with her father, Ms Petrova said, and had been the "perfect kid", getting excellent grades at school.
Ms Skripal, who friends say worked for multinationals including Nike and PepsiCo, was "always smiling, just like her mother", Ms Petrova added.
What else do we know about the family?
Mr Skripal's wife, Liudmila, died in 2012 after suffering from cancer. His elder brother and son have died in the past two years.
Some of the deaths, the family believe, were in suspicious circumstances.
His son, Alexander Skripal, died aged 43 last July in St Petersburg from liver failure. He is buried in Salisbury, close to his mother.
Mr Skripal's family deny that he worked for MI6 and believe that the espionage case was fabricated by Russia.
Has this happened in the UK before?
The possibility of an unknown substance being involved has drawn comparisons with the 2006 poisoning of Alexander Litvinenko.
The former Russian intelligence officer died in London after drinking tea laced with a radioactive substance.
A public inquiry concluded that his killing had probably been carried out with the approval of the Russian President, Vladimir Putin.
An investigation by Buzzfeed News claims that there have been at least 14 deaths in the UK that US officials suspected were connected to Russia.
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