Police and intelligence agencies have failed so far to identify the individual or individuals who carried out the nerve agent attack in Salisbury, the UK’s national security adviser has disclosed.
The comments by Sir Mark Sedwill punctured hopes that the police and other security agencies had pinpointed suspects but were withholding the name or names from the public.
Asked by an MP at a Commons defence committee hearing if he knew the individuals responsible, he replied curtly: “Not yet.”
Sedwill, who coordinates the work of the MI6, MI5, the surveillance agency GCHQ and others, did not elaborate but among problems that have hampered the agencies is a lack of CCTV coverage in Salisbury compared with London. Known Russian spies based in Britain have also been investigated and ruled out.
Sergei Skripal, the former colonel in Russian military intelligence who spied for MI6, is in hospital after being exposed to a nerve agent smeared on the doorknob of his home. His daughter Yulia, who was also exposed to the chemical, has been treated and released.

Sedwill made the rare move in April of releasing classified intelligence on the case. It allegedly showed Russia had tested whether nerve agents could be delivered through door handles and had targeted the email accounts of both the Skripals since at least 2013.
He told the committee on Tuesday the decision to go public had been taken to help counter Russian disinformation.
The attack raised questions about whether the police and MI6, which has a duty to protect agents, should have done more to protect the Skripals. Sedwill said the attack had changed the security services’ appreciation of which dissidents and defectors could be at risk from revenge attacks.
“The police, who are responsible for protective security, and the various agencies alongside them are reviewing the security of all people who might be vulnerable in that way,” Sedwill said.
The bulk of his more than three hours of evidence was devoted to a defence review which is due to be completed by early summer, in particular threats posed by Russia in terms of cyber and conventional military attacks.
Sedwill, who is viewed by some MPs as leaning too much towards the intelligence agencies at the expense of conventional forces, told the committee the UK faced vulnerabilities across its national security system.
He is at the centre of a debate on whether more money should be diverted to cybersecurity or conventional forces.
Replying to a question about where he would spend any extra money, Sedwill declined to be specific, but said: “There are areas of vulnerability, definitely, across our national security commitments that I would want to invest in.”
He added: “There are areas of vulnerability across the entire national security architecture, not just in government. A lot of this is outside government as well.”