"We have not identified the precise source, but we have provided the scientific info to Government who have then used a number of other sources to piece together the conclusions you have come to. He said establishing its origin required "other inputs", some of them intelligence-based, that the Government has access to.
I imagine this is the reason that the UK is not going to be sharing reports with certain countries. We have no obligation to share anything except samples/reports with the OPCW. If we had to share our full report with Russia, it would probably jeopardise the security of UK citizens in Russia working for our intelligence agencies.
That story carries on.
(sauce)
Also:
from (PDF)
This whole story is shady as fuck.