STOPPING PUTIN. If, as seems likely, President Putin ordered the latest assassination attempt on a former Russian spy now living in the UK how should Britain respond?
Sergei Skripal was a highly valued MI6 spy for a decade. He passed valuable information on the GRU, the Russian military intelligence, and was paid through meetings in Spain. He was eventually caught by Russian authorities but later released to the UK under a spy exchange program.
It is possible that Mr Skripal, the former Russian agent turned double-agent for Britain, has continued to advise British Intelligence since his arrival in the UK.
Early indications point to a possible Russia-linked assassination attempt, but authorities need more information about the nerve agent used and where it was made.
Though Russia has denied responsibility, a prominent Russian State TV news presenter this week warned so-called traitors that they would not be able to hide in Britain. Given that the statement was made on State TV, it's possible that Russian authorities approved of this statement.
Whatever the outcomes of the current investigations, Britain must, with the support of her allies, deal harshly though proportionately, with any attempts to kill citizens, foreign or otherwise, on its soil.
What options are there for a British response?
There is some talk of Britain boycotting the World Cup due to take place in Russia. As part of a boycott, Britain may withdraw the English squad from competition, and/or refuse to send any official government representatives. Prince William has already withdrawn from his intended visit.
These options are likely to do little to impress Mr Putin or to dissuade him from potential future attacks of this kind.
Another option open to the British government is to request that July's NATO summit strengthen financial sanctions and travel bans aimed at senior Russian officials.
These have proven painful for prominent Russians in the past, but they do nothing to dent president Putin's standing in the eyes of the Russian people and therefore his position at the top of government.
International opinion matters little to Mr Putin who has previously demonstrated a flagrant disregard for it.
As a proud former KGB man, he may see killing double agents as some form of moral duty and merely a legitimate continuation of Russia’s long-time practice of clandestinely dealing with enemies on foreign soil.
If Britain moves to sanction Russia in more serious ways, Russia will claim victim status as it has done so often in the recent past, even when it has clearly been the aggressor - as with the invasion of eastern Ukraine.
Mr Putin will almost certainly continue as president for the next six years, following presidential elections throughout the next month.
Whatever lies beyond that, he will do everything possible to avoid any international call to account or any stripping of his reportedly enormous financial resources.
In the end, history reveals that those who live by the sword usually die by the sword. Sadly though, some tyrants manage to escape a full measure of justice and continue to meddle in world affairs from the sidelines.
If the Salisbury attack proves to be the responsibility of the Russian authorities, it seems that nothing short of the end of President Putin's rule will stop him engaging in this kind of behaviour.
Even then, history suggests that Russia sees no problem in killing former agents on foreign soil, even when, as in this case, the use of chemical poisons threatens members of the British public.