Police are believed to have identified the suspects behind the Novichok attack on Sergei Skripal and his daughter Yulia.
Mother-of-three Dawn Sturgess died in hospital having been exposed to the nerve agent, while her partner Charlie Rowley, 45, was left fighting for his life after the couple fell ill in Amesbury, Wiltshire.
The Press Association looks at how events unfolded
– Saturday, March 3 2018
Yulia Skripal lands at Heathrow at 2.40pm.
– March 4
Sergei Skripal, 66, and his daughter, 33, are found unconscious on a park bench in Salisbury.
Police say a nerve agent was used to poison the pair, and the case is being treated as attempted murder.
– March 8
Then home secretary Amber Rudd says a Wiltshire police officer, Detective Sergeant Nick Bailey, is seriously ill in hospital.
– March 12
Prime Minister Theresa May tells the House of Commons that the nerve agent is of Russian origin and the Government has concluded it is “highly likely” that Russia is responsible for the poisoning.
– March 14
Mrs May tells MPs the UK will expel 23 Russian diplomats, calling the incident an “unlawful use of force by the Russian state against the UK”.
– March 15
– March 17
Russia announces the expulsion of 23 UK diplomats and says it will shut down the British Council and British Consulate in St Petersburg.
– March 22
Det Sgt Bailey is discharged from hospital, but says in a statement: “Normal life for me will probably never be the same.”
– March 26
Britain’s allies announce that more than 100 Russian agents are being sent home from 22 countries, in what Mrs May calls the “largest collective expulsion of Russian intelligence officers in history”.
– March 28
Scotland Yard reveals Mr Skripal and his daughter first came into contact with the nerve agent at his home.
– April 3
The head of the Porton Down military research facility says his scientists have not verified that the nerve agent used in Salisbury came from Russia.
– April 10
– April 17
The Department for Environment, Food and Rural Affairs says the Novichok used to attack the Skripals was delivered in a “liquid form”.
– May 18
It is announced Mr Skripal has been discharged from Salisbury District Hospital after more than two months of treatment.
– May 26
Businesses in the Maltings area of Salisbury reopen following the attack.
– June 30
Dawn Sturgess and Charlie Rowley fall ill at a property in Muggleton Road in Amesbury, eight miles from Salisbury, and are taken to hospital.
– July 2
Wiltshire Police warn of the dangers of contaminated drugs after the couple fall ill. Detectives believe they may have taken heroin or crack cocaine. The pair are in a serious condition at Salisbury District Hospital.
– July 4
Cordons are put in place at several locations across Amesbury and Salisbury.
Later that night, Scotland Yard reveals that tests show the couple, who have not been formally named, had been exposed to Novichok.
– July 5
Home Secretary Sajid Javid accuses the Russian state of using Britain as a “dumping ground for poison”, and demands that the Kremlin provide an explanation for the two episodes.
– July 6
Forensic investigators in hazardous material suits and gas masks begin searching the building where Ms Sturgess lives.
– July 8
Ms Sturgess dies in hospital following her exposure to Novichok.
– July 9
Scotland Yard launch a murder investigation over the death of Ms Sturgess.
– July 10
Mr Rowley regains consciousness.
– July 11
Investigators speak to Mr Rowley in hospital.
– July 13
Police reveal the source of the Novichok that poisoned Ms Sturgess and her partner was a small bottle found in Mr Rowley’s home.
– July 18
Specialist officers search Queen Elizabeth Gardens in Salisbury, a park at the centre of the poisoning probe.
– July 19
Police are believed to have identified the suspected perpetrators of the Skripal attack, while an inquest is due to open into the death of Ms Sturgess.