As good a place as any for the Salisbury attack.
IMO the objective here was to stoke a response from the UK to boost nationalist support for Putin at home. With an election looming the candidate Navalny whom was disqualified via a 'trial' (discredited by ECHR) has called for Russians to not vote. A very low turnout puts Putin in a weak position domeatically.
The nerve agent used was one of a series developed by the USSR. The UK has reasonably concluded that either the Russian State has attacked the UK or that they have lost control of the nerve agent to outsiders.
Eitherway the Russians should be able to clarify.
My own view is that a better response is to enforce the full Magnitsky sanctions and to boycott and ignore Putin as a world leader. That would hurt him.
https://www.theguardian.com/uk-news/2018/mar/13/russia-demands-nerve-agent-samples-uk-deadline-spy-poisoning