How likely is it that Amesbury novichok is from Skripal batch?

Experts say nerve agent degrades slowly and direct contact is most likely route of exposure

The latest novichok case raises the question of whether the British couple Dawn Sturgess and Charlie Rowley were exposed to the same source of the nerve agent that poisoned the Russian former spy Sergei Skripal and his daughter Yulia in March.

There has been no official comment on this question, but it is scientifically plausible that the agent might persist for long enough, particularly if it was contained in some way.