I can’t really argue with any of that. But equally, details are so scant with desirable political capital available for so many, that it’s possible to make a range of diverse scenarios fit.No evidence that would support a jury conviction of beyong all reasonable doubt is or is likely to be forthcoming...it would be very hard to get such in any event. However there is circumstantial evidence , certainly the type which any police force would have used to bring someone in for questioning...
Had the suspect threatened the victim before ?
Had he the means ?
Had he the opportunity?
Was there a potential upside for the suspect at this time... ?
Could other people have done it?
Was it done by someone else to curry favouritism from the suspect? ... A la Thomas a Becket.
Was it done by another Russian faction to embarrass the leadership?
Was it intended as a provocative gesture?
The remainder of the EU are not all eejits and they will have access to signal intel and gossip from their own sources . In particular the Germans and the Poles very likely have exploitable links. I would not bet against deniable official Russian involvement.
If an accusation of the use of chemical weapons is going to be levelled at a foreign nation, then I believe we need to back that up with more than just a stirring in Theresa May’s drawers. I agree, we should not expect a “beyond reasonable doubt” standard of evidence, but FA evidence doesn’t really cut the mustard.