But Foreign Secretary Boris Johnson knows who ordered the hit.
"We think it overwhelmingly likely that it was (Russian President Vladimir Putin's) decision to direct the use of a nerve agent on the streets of the U.K."
"Unforgivable," says Putin spokesman Dmitry Peskov of the charge, which also defies "common sense." On Sunday, Putin echoed Peskov: "It is just sheer nonsense, complete rubbish, to think that anyone in Russia could do anything like that in the run-up to the presidential election and the World Cup. … It's simply unthinkable."
Putin repeated Russia's offer to assist in the investigation.
But Johnson is not backing down; he is doubling down.
"We gave the Russians every opportunity to come up with an alternative hypothesis … and they haven't," said Johnson. "We actually have evidence … that Russia has not only been investigating the delivery of nerve agents for the purposes of assassination but has also been creating and stockpiling Novichok," the poison used in Salisbury.