Theresa May was backed by over 20 countries and Nato when she accused Russia of using a military grade nerve agent to poison the ex-spy Sergei Skripal and his daughter in the provincial town of Salisbury. But will Britain be more vulnerable to such attacks once it is outside the EU? Siona Jenkins puts the question to Nina Schick, an expert in Russian hybrid warfare at the political consultancy Rasmussen Global, and the FT’s Philip Stephens.