Russian programme 'tested nerve agents with door handles'
Downing Street yesterday took the highly unusual decision to release previously classified information about the Salisbury poisonings in order to debunk Russian propaganda.
In a letter to Jens Stoltenberg, the Nato secretary general, Theresa May's national security adviser gave the most detailed assessment to date of why the UK has blamed Russia for the attack.
The letter from Mark Sedwill set out in clinical terms why Russia had the means, the experience and the motive to carry out the attempted murders of Sergei Skripal and his daughter Yulia.
Scientists at Porton Down defence laboratory identified the nerve agent used in the March 4 attack as belonging to the Novichok family, a finding which was confirmed by Organisation for the Prohibition of Chemical Weapons (OPCW) investigators on Thursday.
Mr Sedwill made clear in his letter that "a combination of credible open-source reporting and intelligence shows that in the 1980s the Soviet Union developed a new class of 'fourth generation' nerve agents, known as Novichoks".
Russia claimed to have destroyed its chemical weapons stockpiles but the letter says it has "produced and stockpiled" small quantities of Novichok "within the last decade".
It added: "The Russian state has previously produced Novichoks and would still be capable of doing so.
"Russia's chemical weapons programme continued after the collapse of the Soviet Union. By 1993, when Russia signed the Chemical Weapons Convention (CWC), it is likely that some Novichoks had passed acceptance testing, allowing their use by the Russian military.
"Russia further developed some Novichoks after ratifying the convention. It is highly unlikely that any former Soviet republic (other than Russia) pursued an offensive chemical weapons programme after independence. It is unlikely that Novichoks could be made and deployed by non-state actors (eg a criminal or terrorist group), especially at the level of purity confirmed by OPCW."
The origin of the nerve agent has been a source of intense speculation.
The failure to specify exactly where the substance was made has been used by critics to question the UK government's decision to formally blame Russia for the poisonings.
But Mr Sedwill's letter suggested the nerve agent used was most likely to have been made at a laboratory in Shikhany, near Volgograd, a branch of the State Institute for Organic Chemistry and Technology.
It states it is "highly likely that Novichoks were developed to prevent detection by the West and to circumvent international chemical weapons controls".
Russian President Vladimir Putin, who served as a KGB operative between 1975 and 1991, said Moscow "does not possess such agents" and dismissed claims of Russia being behind the attack as "nonsense".
But Mr Sedwill's letter claimed that "in the mid-2000s, President Putin was closely involved in the Russian chemical weapons programme".
The Kremlin has also been linked to the deaths of numerous prominent Russian dissidents and Mr Sedwill said "Russia has a proven record of conducting state-sponsored assassination".
Police have said that the highest concentrations of the Novichok nerve agent were found on Mr Skripal's front door, suggesting that was where the nerve agent had been deposited.
Mr Sedwill revealed in his letter: "During the 2000s, Russia commenced a programme to test means of delivering chemical warfare agents. This programme subsequently included investigation of ways of delivering nerve agents, including by application to door handles."
Perhaps the most explosive claim in his dossier was that Russian security services had hacked Yulia Skripal's email accounts for at least five years before she and her father were found slumped on a park bench in Salisbury.
Mr Sedwill concluded: "We therefore continue to judge that only Russia has the technical means, operational experience and motive for the attack on the Skripals and that it is highly likely that the Russian state was responsible.
"There is no plausible alternative explanation."