We need to recap briefly the similarities between Alexander Litvinenko and Sergei Skripal, because they are stark.

Both served in the Russian security services; both faced prosecution in Russia; both found sanctuary in Britain; both co-operated with British intelligence agencies. And both were attacked with rare poisons, of kinds available only to governments. The only important difference is that Litvinenko’s murderers were successful, while Skripal is still fighting for his life.

Suspicion is strong that Litvinenko was killed because he was revealing secrets about the Kremlin’s business interests and the inquiry into his 2006 murder was pretty categorical about the identity of the poisoner. Judge Robert Owen, in his ruling two years ago, concluded there was a “strong probability” that the FSB had sent the two assassins who came from Russia to murder Litvinenko, in an operation “probably approved” by Vladimir Putin.

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Considering the similarities between the two poisonings and the two victims, it is not alarmist to ask whether the same man also stands behind this new attempted murder. As Michael McFaul, a Russianist who tried and failed to improve US-Russia relations while President Barack Obama’s ambassador to Moscow, put it: “Is there anyone else, besides the Russian government, who would have a motive for trying to kill Skripal?”

That is the six-billion-rouble question. Poisoning one ex-spy in Britain might be a one-off, an exceptional act of retribution. But if the Kremlin has poisoned a second ex-spy in Britain, that looks like a policy. It was pure good fortune that no bystanders were harmed when Litvinenko was murdered, considering how carelessly his killers splashed polonium-210 around. The residents of Salisbury were not so lucky and no government can tolerate such reckless indifference to the wellbeing of its citizens.

Timeline Poisoned umbrellas and polonium: Russian-linked UK deaths Show Hide Georgi Markov In one of the most chilling episodes of the cold war, the Bulgarian dissident was poisoned with a specially adapted umbrella on Waterloo Bridge. As he waited for a bus, Markov felt a sharp prick in his leg. The opposition activist, who was an irritant to the communist government of Bulgaria, died three days later. A deadly pellet containing ricin was found in his skin. His unknown assassin is thought to have been from the secret services in Bulgaria. Alexander Litvinenko The fatal poisoning of the former FSB officer sparked an international incident. Litvinenko fell ill after drinking tea laced with radioactive polonium. He met his killers in a bar of the Millennium hotel in Mayfair. The pair were Andrei Lugovoi – a former KGB officer turned businessman, who is now a deputy in Russia’s state Duma – and Dmitry Kovtun, a childhood friend of Lugovoi’s from a Soviet military family. Putin denied all involvement and refused to extradite either of the killers. German Gorbuntsov The exiled Russian banker survived an attempt on his life as he got out of a cab in east London. He was shot four times with a silenced pistol. He had been involved in a bitter dispute with two former business partners. Alexander Perepilichnyy The businessman collapsed while running near his home in Surrey. Traces of a chemical that can be found in the poisonous plant gelsemium were later found in his stomach. Before his death, Perepilichnyy was helping a specialist investment firm uncover a $230m Russian money-laundering operation, a pre-inquest hearing was told. Hermitage Capital Management claimed that Perepilichnyy could have been deliberately killed for helping it uncover the scam involving Russian officials. He may have eaten a popular Russian dish containing the herb sorrel on the day of his death, which could have been poisoned. Boris Berezovsky The exiled billionaire was found hanged in an apparent suicide after he had spent more than decade waging a high-profile media battle against his one-time protege Putin. A coroner recorded an open verdict after hearing conflicting expert evidence about the way he died. A pathologist who conducted a postmortem examination on the businessman’s body said he could not rule out murder. Scot Young An associate of Berezovsky whom he helped to launder money, he was found impaled on railings after he fell from a fourth-floor flat in central London. A coroner ruled that there was insufficient evidence of suicide. But Young, who was sent to prison in January 2013 for repeatedly refusing to reveal his finances during a divorce row, told his partner he was going to jump out of the window moments before he was found.

Skripal poisoning Sergei Skripal and his daughter Yulia were were found unconscious on a bench in the Maltings shopping centre in Salisbury after 'suspected exposure to an unknown substance' which was later identified as chemical weapon novichok. In the aftermath Theresa May blamed Vladimir Putin and expelled 23 Russian diplomats who were suspected of spying. Two Russian men using the identities Ruslan Boshirov and Alexander Petrov were named as suspects. They appeared on Russian TV to protest their innocence.

The Skripals survived. However a local woman, Dawn Sturgess, died after spraying novichok on her wrists from a fake Nina Ricci perfume bottle converted into a dispenser, which had been recovered from a skip by her partner Charlie Rowley.

It appears that Britain’s spies told the Tony Blair government the Litvinenko murder had been ordered from the highest levels of the Russian government long before the rest of us had that confirmed. But politicians felt unable to respond robustly because they wanted to retain Moscow’s co-operation in security matters. “They are too important for us to fall out with,” an unnamed minister told the Sunday Times before Litvinenko’s lead-lined coffin had even been buried.

We eventually expelled a handful of diplomats, after Russia refused to extradite the murderers, but Whitehall’s instinct remained to try to smooth things over, like a hostess offering canapes to a fractious party guest. After the coalition came to power in 2010, David Cameron visited Moscow to reset relations, in a policy mirrored by McFaul and Obama. They believed that if they just trusted Putin he would prove trustworthy: offer him enough vol-au-vents and he would calm down. The alternative was too ghastly to contemplate.

Trump can be counted on to troll Sadiq Khan if there’s a terrorist attack in London... he is yet to bother tweeting about Sergei Skripal

In 2014, Putin annexed Crimea and sent his implausibly deniable proxies into eastern Ukraine, where they shot down a civilian airliner, killing 298 people. Then Russian hackers broke into the Democratic party’s servers and in 2016 distributed its emails in an operation transparently aimed at influencing the American people’s democratic choice. The party guest was not mollified, smashed up the living room with a golf club and pushed the vicar into the pool.

It is a sign of how low relations have sunk between Russia and the west that there was an inquiry into the death of Litvinenko at all. As home secretary, Theresa May opposed publicly airing the evidence that Russia had killed a British citizen in the first deliberate nuclear attack since Nagasaki, to try to protect relations with Russia. It was only after Crimea that she gave way; there were no relations left worth saving.

Play Video 2:03 Who is the Salisbury spy Sergei Skripal? – video explainer

This bad relationship should make sanctioning Putin’s government easier for our politicians to stomach, but in other ways, May’s job now is significantly harder than Blair’s was in 2006. For one thing, we no longer have a reliable ally in Washington. Donald Trump can be counted on to troll Sadiq Khan whenever there’s a terrorist attack in London but he is yet to bother tweeting about Sergei Skripal, his daughter, Yulia, DS Nick Bailey or the 18 other people affected by the nerve agent used last Sunday.

Trump’s indifference extends to his own country’s Russia problem. Last year, Congress asked the White House to study which Kremlin insiders could be targeted by sanctions, so it copied out a list from Forbes magazine. It would, in short, be foolish to rely on Washington for help against Putin. If US assistance is not forthcoming, the government needs to work with our European allies. It is a shame that so much of our diplomatic capital has been squandered on Brexit, instead of being held back for something important.

Facebook Twitter Pinterest Suspicion is strong that Alexander Litvinenko was poisoned because he was revealing secrets about the Kremlin’s business interests. Photograph: Natasja Weitsz/Channel 4 Picture Publicity

But acting alone is still possible. South-east England is a favourite playground of rich Russians. They keep their houses here, their children here, they float their companies on our stock exchange and they don’t make a secret of it. You’re not rich in Russia without being friends with Putin – in fact, there is a remarkably close correlation between the two groups – so if May’s government wants to send a message to the Russian president, it could cancel the visas of the members of his inner circle and, perhaps, try out the potency of its new “unexplained wealth orders”, by freezing their property. Then it should dismantle the mechanisms with which they launder their money.

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As one MP told me yesterday: “We need to be arseholes, we need to be tough on the aristocrats and we need to kick their kids out.” This is the time to ask the party guest to leave. Putin’s people care most about getting rich and the only way to change their mind is to cost them money.

• Oliver Bullough is a journalist and the author of two nonfiction books about Russian history and politics: The Last Man in Russia and Let Our Fame Be Great