Mother-of-three Dawn Sturgess has died in hospital having been exposed to nerve agent Novichok – just four months after former Russian spy Sergei Skripal and his daughter Yulia were poisoned.
Ms Sturgess’s partner Charlie Rowley, 45, is still in a critical condition after the couple fell ill in Amesbury, Wiltshire, last Saturday.
The Press Association looks at how events have unfolded.
Saturday, March 3 2018<br>Ms Skripal lands at Heathrow at 2.40pm.
March 4<br>Mr Skripal, 66, and his daughter, 33, are found unconscious on a park bench in Salisbury.
March 5<br>Mr Skripal and his daughter are publicly identified and declared “critically ill” in hospital.
March 6<br>Speculation mounts about Russian involvement in the incident and counter-terrorism officers take over the investigation. The Russian Embassy accuses the media and Government of “anti-Russian” sentiment.
March 7<br>Police say a nerve agent was used to poison the pair, and the case is being treated as attempted murder.
March 8<br>Then home secretary Amber Rudd says a Wiltshire police officer, Detective Sergeant Nick Bailey, is seriously ill in hospital.
March 11<br>Up to 500 diners and pub-goers are told to wash clothes and other items after traces of a nerve agent are found in The Mill pub and the nearby Zizzi restaurant – venues visited by the Skripals.
March 12<br>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 13<br>The Russian Embassy in the UK says Moscow “will not respond to London’s ultimatum”. It emerges that 38 people received medical treatment in the aftermath of the attack.
March 14<br>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<br>Leaders of Britain, the US, Germany and France issue a joint statement blaming Russia for the attack.
March 17<br>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<br>Det Sgt Bailey is discharged from hospital, but says in a statement: “Normal life for me will probably never be the same.”
March 26<br>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<br>Scotland Yard reveals Mr Skripal and his daughter first came into contact with the nerve agent at his home.
April 3<br>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<br>The hospital announces Ms Skripal has been discharged from hospital.
April 17<br>The Department for Environment, Food and Rural Affairs says the Novichok used to attack the Skripals was delivered in a “liquid form”.
May 18<br>It is announced Mr Skripal has been discharged from Salisbury District Hospital after more than two months of treatment.
May 26<br>Businesses in the Maltings area of Salisbury reopen following the attack.
June 4<br>Wiltshire Police’s response to the attack in Salisbury is expected to cost £7.5 million.
June 24<br>Homes, cars and possessions belonging to Mr Skripal and Det Sgt Bailey will be bought by taxpayers in a £1 million deal, it has been reported.
June 29<br>Britain has exterminated evidence related to the poisonings and has benefited politically from the incident, Russia’s foreign minister Sergey Lavrov has claimed.
June 30:<br>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<br>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<br>In the early hours, police declare a “major incident” after revealing that Ms Sturgess and Mr Rowley have been exposed to an “unknown substance”. 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. Police were unable to say whether it was the same batch that the Skripals were exposed to.
July 5<br>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<br>Forensic investigators in hazardous material suits and gas masks begin searching the building where Ms Sturgess lives.
July 7<br>A police officer attends hospital over concerns of a possible exposure to Novichok – he later tests negative for the nerve agent.
July 8<br>Mr Javid, on a visit to Wiltshire, says there will be no fresh sanctions against Russia over the attacks.
Ms Sturgess dies in hospital following her exposure to Novichok.