He certainly looks the part. Vladimir Putin is a textbook villain, with his piggy eyes, his puffy face, the result perhaps of steroid use or inexpert plastic surgery. He is a narcissistic authoritarian who in his 18 years in power, has made a sham of Russian democracy, suppressed free speech, condoned homophobia, engaged in military adventurism in Ukraine and allied with deeply unpleasant characters like Syria's Bashir Assad. Vladimir Putin is quite capable of ordering the liquidation of his opponents, and passed legislation which effectively authorised the killing of Russian traitors abroad. The circumstantial evidence is compelling that he was behind the attempted murder of the former double agent, Sergei Skripal and his daughter in a Salisbury shopping centre.

But in a court of law, this would not be enough to convict him, and there are very odd things about this case. It doesn't make any political sense for a start. Skripal was a very small time spy who presented no threat to Russia and had no recent intelligence to impart about its clandestine activities. He was not a figure who occupied a prominent place in Russian demonology about the west. In no way was he the Russian equivalent of celebrity traitors like Guy Burgess or Kim Philby.

If Vladimir Putin did authorise his assassination it was not just abominable and cowardly but an act of geopolitical stupidity which even the dumbest dictator would surely see as counterproductive. It is as an act of war against a sovereign nation in defiance of international law and the global ban on use of chemical weapons. The poisoning has emboldened Russia's critics, guaranteed further economic sanctions, made Russia a pariah state, and reunited the nations of Nato, which had been in some disarray following the election of President Trump who is an instinctive isolationist. All this was foreseeable.

The Russian President is a national chauvinist who has dedicated his regime to restoring Russian prestige - to Make Russia Great Again. Fresh from his success in Syria, where he outplayed the West by backing the Assad regime in its war against Islamic fundamentalists and other rebel forces, Putin had been walking tall on the international stage. Attempting to kill an obscure pensioner and his daughter in a quiet English market town is not the act of a Great Power, but of a delinquent state. Putin was looking to this summer's Moscow World Cup as a showcase for himself and his resurgent Russia, but his actions have ensured that the second biggest sporting event on the planet will now be a shambles if it happens at all.

We are told that Putin needed to kill Sergei Skripal in order to boost his popularity in the Russian elections. This is the oddest reason of all, since Putin is already all too worryingly popular in Russia (since the days of Adolf Hitler authoritarians have often proved to be so). He is guaranteed victory since most of the opposition has been suppressed. The murder of Skripal was hardly reported in the Russian media until Theresa May made her ultimatum on Wednesday and then expelled 23 Russian diplomats. Maybe some Russian voters will say, “good riddance” to this obscure spy, but as electoral catnip it is miserable compared with the annexing of Crimea, or Putin's recent announcement of his “unstoppable” nuclear cruise missile.

Of course, I don't have any alternative explanation, other than the obvious ones: that perhaps rogue elements in the Russian intelligence community were settling old scores; another nation or group wanted to frame Russia; or that some oligarch had a personal beef with Skripal. London has certainly become a playground for Russian plutocrats who are often ruthless individuals who conduct vendettas. But even the oligarch theory makes little sense. A rare nerve agent seems an unlikely weapon for a Mafia-style killing. And why would your average oligarch want to frame Putin in this elaborate manner? The poisoning, which recklessly endangered civilians, can only make life more difficult for the rich Russians with dodgy backgrounds who cruise central London in their black Mercs. There have already been demands that oligarch cash should be seized and that the British Conservative Party, which received a thick wodge of it, should hand it back and expel the donors.

The Russian state is certainly the most likely suspect. The nerve agent used - 'Novichoks' - was developed in Russia in the early 1990s and seems like the kind of weapon that only a state-backed security service would have access to. Social media has been buzzing with instant experts on chemical weapons who have 'proved' that the nerve agent came from Russia and, like Boris Johnson, claim that Putin was the only person who could have ordered the use of it. But no such proof exists yet. The real experts, including, Ralf Trapp, who helped set up the Organisation for the Prohibition of Chemical Weapons (OPCW), have told BBC radio that many countries know how to make novichoks. He did not rule out the possibility that some of it leached out of Russia in the early 1990s, when chemical weapons establishments were being ransacked for anything saleable on the international markets.

Would a rival nation or terrorist group go to such lengths to damage Putin? Some Chechens, Ukrainians and South Georgians might have the motivation, since Putin invaded their countries, but would they have the means? I do not subscribe to the paranoid theory that MI5 or the US intelligence services had committed this act as a false flag for the simple reason that in democracies it is very difficult to keep such devilish ploys secret. The British secret services may have executed people in the past, but they don't do it in English shopping precincts.

So the finger of suspicion points at Russia, but with real questions about motives and as yet a lack of firm evidence. Mind you, none of this has mattered to the claque of superannuated cold warriors and sabre-rattlers in the UK parliament and media for whom this is another Red Dawn, a chance to refight the war against communism. Jeremy Corbyn was portrayed as 'Kremlin Stooge' for warning against a rush to judgement. But he is surely right to be cautious. We learned from the WMD debacle in Iraq, that making rash judgement calls about such weapons of mass destruction can lead to disastrous consequences. If Putin is indeed responsible, it doesn't help to act first and seek evidence later.

Theresa May clearly saw an opportunity to divert attention from Brexit by ramping up the anti-Russian rhetoric, and the Labour leader's enemies in his own party were primed to use this atrocity to condemn Corbyn as being soft on communism, even though Communist Russia no longer exists. This is how wars start – generally by accident. Britain was too impatient to wait for the OPCW to investigate thoroughly this breach of the ban on chemical weapons because Theresa May doesn't want to appear soft. Yet acting calmly and methodically is not a sign of weakness. Quite the reverse: it is always a sign of strength to observe due process.

Evidence speaks more strongly than denunciation. The UK Defence Sectary, Gavin Williamson, made an ass of himself by petulantly announcing that “Russia should shut up and go away”. He should get a grip. You don't deal with tyrants like Vladimir Putin by aping his own tactics.