From Moon of Alabama:

Neither in its press statement nor in its public Summary Report (pdf) does the OPCW speak of finding a ‘nerve agent’. But what is this ‘toxic chemical’? Saxitoxin, a natural poison that causes Paralytic Shellfish Poisoning (PSP) which would be consistent with the symptoms the Skripals showed shortly after eating a Risotto Pesce with mussels? Or some artificial agent designed as chemical weapon? Neither the OPCW nor Porton Down will say.

From the comments:

All the evidence seems to point to both Skripals being long since dead…

If the nerve agent was pure, as the OPCW appears to claim, then the attack would have to have taken place on the park bench – which for many reasons is infinitely more plausible from the point of view of the timeline of the Skripals’ response to the poisonings. All incriminating cctv evidence would have been destroyed already…

Sergei was obviously the prime source of the Steele dossier, and had to be silenced at all costs…

Also, if the Skripal’s are dead (as seems likely) and were poisoned on the park bench, SD Nick Bailey seems to be a prime suspect…

Here’s the nub of the proposition. How to get the Novichok into the now hospitalised Skripal’s bloodstreams…

The fiance is also reported missing.