The chemical research facility of Porton Down has been unable to establish that the nerve gas with which the Skripals were poisoned came from Russia. In an interview with Sky News, director Gary Aitkenhead says that the nerve gas used was indeed novichok or a product derived from it, but that the source could not be identified.
Aitkenhead refutes the possibility that the nerve gas would have come from its own research facility, a scenario deemed possible by Russia. It remains unclear where the nerve gas comes from and who ultimately used it to poison the Skripals. According to the Russian government, the Novichok nerve gas used can be produced in twenty different countries.
According to the British government there are strong suspicions and indications that Russia should be held responsible for this attack, an accusation taken over by several allies and leading to a large-scale expulsion of Russian diplomats.