I’m not an alarmist by nature, but I must admit Putin’s rant has left me fearful . . .

WHEN the possibly deranged dictator of a barbaric regime threatens a nuclear strike against the West, it is wise to take him seriously.

That is what Vladimir Putin said yesterday, while announcing the mobilisation of 300,000 reservists to help shore up Russia’s flagging war in Ukraine.

Threats of nuclear retaliation against the West have been issued in the past by Soviet and Russian leaders but never — not even at the height of the Cold War — has there been one as explicit as this.

Putin declared: ‘ We will use all available means to protect Russia and our people — this is not a bluff . . . I shall stress — by all means available to us. Those trying to blackmail us with nuclear weapons should know that the tables can turn on them.’

In case there was any room for doubt, a former close adviser of Putin’s, Sergei Markov, filled in some details on yesterday’s Radio 4 Today programme when he warned that ‘your cities will be targeted’.

This is what Markov said in his spinechilling rant: ‘If Great Britain will continue to be [the] aggressor against Russia . . . if Prime Minister Liz Truss still has a plan to destroy Russia, people in London should understand the threat [of nuclear weapons].’

Unhinged? Without any doubt. But it would be rash of our political leaders and of the general public to dismiss these outpourings as empty threats. I only wish that they were.

It’s not the first time the Putin regime has spoken in such terms. Back in April, Sergei Lavrov, Putin’s puppet foreign minister, warned that if Nato continued to provide military aid to Ukraine, there would be a ‘considerable threat’ of a nuclear conflict.

On that occasion, Boris Johnson was asked on TalkTV whether he shared the concerns of some analysts about the possibility of nuclear war. He replied — unwisely, perhaps: ‘No, I don’t.’

CAN anything be done to obviate the danger? The terrible answer is that I don’t think it can. Putin may, or may not, be mad. But it is certain that he has given up all pretence that his regime adheres in the smallest degree to standards of decency and honesty.

Before the war began, I argued in these pages that Russia had something of a case inasmuch as there were undoubtedly ethnic Russians in eastern Ukraine who preferred to be ruled by Moscow than Kyiv. That argument, though correct at the time, is now ancient history.

For by invading Ukraine, and prosecuting the war in such a brutal way, Putin has established that he is both unbalanced and inhumane. Some of the war crimes committed by Russian soldiers stand comparison with the worst Nazi atrocities.

Putin has deliberately killed thousands of Ukrainian civilians, and forcibly deported thousands more to Russia. There is ample evidence of widespread torture and murder.

In a pine forest at the edge of Izyum in eastern Ukraine, which has recently been taken back from Russian hands, 445 graves have just been found, some containing more than one body. Many are said to be civilians, and there are women and children among them. In some cases there is evidence of torture.

This is barbarism on an epic scale. It confirms, I believe, that Putin is beyond the pale of civilised behaviour. Moreover, a despot who can torture and murder innocent civilians may have no moral qualms about using nuclear weapons.

The truth is that we can’t abandon Ukraine. We must continue to provide weapons to its armed forces — Britain is the second largest supplier of arms after the United States — because the country is engaged in a fight against an evil aggressor.

But there is more to it than that. If we had not supported Ukraine, Putin’s forces would have also menaced the Baltic states and Poland, and potentially the rest of Eastern Europe. In helping Ukraine to defend itself we are defending ourselves.

So there is no easy answer to my question as to whether anything can be done to decrease the danger of a Russian nuclear attack. In these circumstances it would be both morally unthinkable, and also contrary to our interests, to forsake Ukraine.

We must be strong. That means increasing our defence expenditure as Liz Truss has undertaken to do, promising an almost 50 per cent rise by the end of the decade. But this, of course, is a slow process which won’t yield instant improvements.

We can also place some faith in the traditional doctrine of nuclear deterrence, which holds water if a potential adversary is essentially rational. I ardently hope, despite evidence to the contrary, that Vladimir Putin still is.

Although Russia has vastly more nuclear weapons than we do (the number of our warheads was rashly reduced by the Blair government), Britain still has the nuclear firepower to destroy Moscow and a large number of Russian cities.

Moreover, our closest ally, the United States, has a nuclear arsenal roughly equal in size to Russia’s, and in terms of technical prowess it is probably far superior.

THESE are grim calculations, and I regret having to make them. My point is that in a rational world — and, despite everything, the Cold War played out in a rational world — Vladimir Putin wouldn’t unleash a nuclear attack against Britain or any other western country.

But I am afraid we can’t rule out the possibility, however distant, that he might — which is why we find ourselves in the greatest danger since the end of World War II.

Some experts believe that while it is unlikely that Putin would use nuclear weapons against any western country for fear of massive retaliation, he might employ so- called battlefield nuclear weapons ( which are much more limited, and so less lethal, in their effects) against Ukrainian troops.

Even that, though, would be a perilous step since the use of any nuclear weapons might quickly escalate. What would the United States do if Russia used battlefield nuclear weapons in Ukraine?

Here I hope to be forgiven for observing that the intellectually somewhat dicky 79-yearold Joe Biden doesn’t appear the most dependable or best informed leader the free world has ever had. All that can be said is that, in this crisis, he is preferable to Donald Trump.

Our best bet may be that, as it becomes clearer to Russians that their country is losing the war in Ukraine, and thousands of Russian lives are being sacrificed, there will be a putsch against Putin before he does anything truly stupid. This, though, is beyond our control. And it might not happen.

I am not by nature an alarmist but I admit to feeling fearful. Rationality may well prevail. However, there are, alas, many examples in history — Hitler’s doomed invasion of Russia in 1941 is a good one — of despots jettisoning all good sense.

We can only hope that our leaders — unlike Boris Johnson in April — are aware of the great dangers we face. I fear the British public hasn’t yet woken up to them.

All our silly squabbles concerning strikes, and even our justified fears about the soaring price of energy, could quite soon seem utterly trivial in the light of an unthinkable — but not impossible — catastrophe.