Novichok is so secret that we do not know its exact chemical makeup. That is how we were able to identify it so quickly.
https:// www.theverge.com/2018/3/14/17120696/russian-novichok-skripal-nerve-agent-chemical-weapon-poisoning-england
Theresa May has good reason to be angry at Russia. They let MI6 believe that Skripal was working for Britain and so the UK rook him in. Now they learned that Skripal has been spying for Russia all along, so MI6 poisoned him with something that kills slowly, locked hm away in a hospital to die, and pinned the whole thing on Russia.
Espionage games writ large.
Nothing about the UK Skripal and other Russian spy events are what they seem. All we can really see from the outside is that things are happening. We have no real way to tell what is actually going on, who is attacking who, and so on. Everything made public is filled with false leads and disinformation.