The response to the Kremlin-backed murder of a former Russian spy in London more than a decade ago was to talk tough but do very little to punish those implicated in the crime.

Diplomatic relations and intelligence sharing were put on ice but punishments, such as sanctions on the two men accused of using polonium-210 to kill Alexander Litvinenko, fell far short of the wishes of his widow to see President Putin held to account. This means there is no deterrence to stop him authorising another assassination, as he is thought “probably” to have done in the case of Litvinenko.

Russian security experts said the illness of Sergei Skripal and his daughter, Yulia, was most likely to have been caused by foul play. If