The former chief medical officer for England said she had experienced nightmares about someone picking up discarded nerve agent after the poisoning of a former spy.
Sergei Skirpal and his daughter Yulia were poisoned by Novichok in Salisbury in March 2018.
The attempted murders were followed by the death of Dawn Sturgess, 44, in July of that year, after she was exposed to the chemical weapon which was left in a discarded perfume bottle.
The inquiry into Ms Sturgess' death heard how Dame Sally Davies had worried about someone picking up Novichok from the moment she knew "Russian agents had been involved" in the incident.