The news that a former Russian spy is in hospital amid mysterious circumstances has prompted comparisons with the death of Alexander Litvinenko - including from his widow.
A Russian dissident who became a British citizen, Mr Litvinenko died aged 43 in November 2006, three weeks after he drank tea laced with radioactive polonium-210 at the Millennium Hotel in Mayfair, central London.
A public inquiry concluded in 2016 that the killing had "probably" been carried out with the approval of the Russian president.
As Sergei Skripal, 66, fought for his life after being found unconscious on a bench in Salisbury, Marina Litvinenko told BBC Radio 4's World Tonight: "It's like deja vu, (like) what happened to me 11 years ago."
She added: "In Russia it is still (an) old-fashioned and old-style KGB system... It's still all the same. If there is an order to kill somebody it will happen."
Police have said they are as yet "unable to ascertain" whether Mr Skripal had been a victim of crime, while the a Russian Embassy spokesman said: "Neither relatives nor legal representatives of the said person, nor the British authorities have addressed the embassy in this regard."
The Litvinenko inquiry, headed by the former high court judge Sir Robert Owen, found two Russian men - Andrei Lugovoi and Dmitri Kovtun - had deliberately poisoned their victim, leading to an agonising death.
It said the use of the radioactive substance - which could only have come from a nuclear reactor - was a "strong indicator" of state involvement and that the two men had probably been acting under the direction of the FSB, Russia's state agency.
Possible motives included Mr Litvinenko's work for British intelligence agencies, his criticism of the FSB, and his association with other Russian dissidents, while it said there was also a "personal dimension" to the antagonism between him and Mr Putin.
International arrest warrants issued for Mr Lugovoi and Mr Kovtun remain in force although Russia continues to refuse their extradition.
Mr Putin had refused to accept the inquiry's findings.
Meanwhile, a coroner examining the death of a wealthy Russian whistleblower warned last year of the danger of getting "caught up in conspiracy theories".
The inquest into the death of Alexander Perepilichnyy is looking at whether he died from natural causes or was poisoned before he collapsed while out jogging near his home in Weybridge, Surrey, in November 2012.
At the time, the 44-year-old father-of-two was allegedly helping specialist investment firm Hermitage Capital Management uncover a $230 million (£150 million) Russian money-laundering operation.
He had also recently taken out £3.5 million of life insurance and applied for another £5 million worth of policies, the inquest at the Old Bailey heard last June.
Lawyers for Hermitage previously claimed that Mr Perepilichnyy could have been deliberately killed and had been on an underworld "hit list".
Detective Superintendent Ian Pollard, of Surrey Police, said he did not think Mr Perepilichnyy was under threat and he found no link to foreign crime gangs.
The inquest is set to resume in mid-April.
And the circumstances of the death of Russian oligarch Boris Berezovsky remained uncertain after a coroner recorded an open verdict in March 2014.
After summing up the two days of "contradictory" evidence, Berkshire coroner Peter Bedford said he could not prove beyond all reasonable doubt that the businessman either took his own life or was unlawfully killed.
The body of the former Kremlin insider was discovered slumped on the bathroom floor at his ex-wife's luxury property in Ascot, Berkshire, with a ligature wound to his neck on March 23 last year.
Although there were suggestions that the 67-year-old - who had survived at least two assassination attempts - was murdered, police did not find any evidence of foul play.