I've seen no evidence whatsoever that the alleged attack was carried out by Russia.
Novichok agents were developed in the 1970s, have been the topic of many publications, and the simple and widely-known chemical structures of any number of them could be made by chemists from any country or group willing to take the risk to make them.
https://en.wikipedia.org/wiki/Novichok_agent
If Britain is intent on dragging NATO into this, as it seems like it might be, there had better be far more compelling evidence of Russia's involvement than the weak drivel published to date.
https://www.theguardian.com/uk-news/2018/mar/13/nerve-agent-...
Remember yellowcake?