Following this article, why didn't the UK release its results about Novichok when Russia asked for it?
Because the disclosure of intermediate results of the ongoing investigation would also disclose:
- the methodology of chemical analysis and the recent technology capabilities available to this particular investigation and to the secret services in general;
- information about what the investigation knows so far and — most importantly — what it does not know yet; events, collected physical evidence, list of suspected people, etc.
which in turn would let the suspects to:
- build the defense strategy;
- orchestrate the covert operation in propaganda outlets;
- try to salvage agents who have been involved but not under investigation yet;
- improve their further development of WMD by directing their effort toward developing substances less detectable with current technology.
One thing is when the suspect says, 'it's a horrible tragedy; let us work together to figure out what happened and who's guilty; we provide you with all we know, please also share what you know', and another thing is when they say, 'one should not threaten a nuclear armed country'.