Sergei and Yulia Skripal were poisoned by an immobilizing substance called 3-Quincucnidnyl Benzilat (BZ), Russian Foreign Minister Sergei Lavrov said. It was discovered by the Swiss laboratory Spiez, an internationally recognized institution. At the same time, the report says that this substance does not come from Russia but was used by the United States and the United Kingdom.
No evidence given. The laboratory has answered that is has "no doubt that Porton Down has identified Novichock". https://twitter.com/SpiezLab/status/985243574123057152
The OPCW have confirmed the UK findings in the case. "The results of the analysis by the OPCW designated laboratories of environmental and biomedical samples collected by the OPCW team confirm the findings of the United Kingdom relating to the identity of the toxic chemical that was used in Salisbury and severely injured three people." https://www.opcw.org/news/article/opcw-issues-report-on-technical-assistance-requested-by-the-united-kingdom/