Porton Down scientists can't identify Novichok as Russian made, or its country of origin... analysis. 1) It doesn't contradict May's 26 March statement but gives its components different weight (see screengrab) Thread.... 
2/ They ID'd Novichok; there is a pattern and they have "information indicating" Russia stockpiled a small amount of Novichok for assasination purposes. This third deductive step now becomes more important in pinning attack on Russia.
3/ Lots of experts been briefing "they will identify the nerve agent's production facility". Clearly this not possible in this case. But it makes OPCW involvement more important.
4/ Here's what @jeremycorbyn asked May: "Has high-resolution trace analysis been run on a sample of the nerve agent, and has that revealed any evidence as to the location of its production or the identity of its perpetrators?"
5/ May did not directly answer this. She did not address the clear question Corbyn asked about the evidence of the production. The Russian state link is a deduction from other evidence.
6/ We have to be prepared to accept such deductions/analysis on trust - despite what happened with Iraq. But it means the Russian link comes from "information indicating"... i.e. SIGINT, HUMINT etc not the sample.
7/ However, Boris Johnson claimed to have "asked the guy himself" if Porton Down were sure it came from Russia. "He said there's no doubt". This needs to be clarified.
8/ The Kremlin trolls, bots and fake news purveyors will have a field day with this but the problems are of HMG's own making. May was asked a clear question - ducked it; Johnson seems to have been too categoric...
9/ My assumption is either it was a Russian state action, or an unauthorised freelance job or - an outside chance - they lost control of the substance: but that's why we have HM Loyal Opposition: to ask questions.
10/ Corbyn asked a laser-accurate question and it was dodged. If Labour MPs had a) noticed b) piled in for clarification instead of attacking their own leader on 26/3... May might have been forced to clarify earlier.
