At the heart of the West’s response to Russia’s invasion of Ukraine sits an ambiguity that it is convenient, perhaps even necessary, for our political leaders to maintain. If we can turn the clock back on Putin’s foolish endeavour – if he can be persuaded to withdraw his troops, disavow Russia’s territorial ambitions and return to the status quo ante – then, with Ukraine again an autonomous and independent country, does the West also return to the status quo ante in our own dealings with Russia?

The answer to this question matters enormously, because if we’re holding out to Moscow an opportunity to return to the same footing as in former times, resuming (as it were) normal service, then we can offer a much more attractive reward for its retreat from Ukraine. But should we?

I will not bore you with a list you already know: of sanctions we have so far imposed on Russia, of which surely the most important is the shutting of the Russo-German Nord Stream 2 pipeline. The net has further to tighten on Russian energy exports, as the free world seeks alternative supplies. Russia lives by her export of resources for which we must now seek alternative sources. Which of these sanctions is the West prepared to reverse if Moscow retreats from Ukraine? It depends on whether the West’s response to Russian aggression is about modifying her behaviour, or about regime change.

We shy away from the expression ‘regime change’ because of its association with Iraq, Syria and Libya and, more generally, liberal interventionism. But in these cases the West was essentially the aggressor. In the Balkans, by contrast, the aggressor was Slobodan Milosevic and we had no thought of reforming him, only of removing him. It is now Moscow that has picked the fight: the work of one man, Vladimir Putin. He is a war criminal – and (just as important) we know he’s utterly untrustworthy. Can it really be the West’s ambition to change the nature of his leadership or even, in the longer term, to constrain his behaviour? Though I’ve always thought Putin’s ambitions to absorb the Baltic states were dreams, not plans, the same may not be true of (for instance) Georgia or Moldova. Do we honestly think a ceasefire and compromise agreement could be drawn up that left Putin as Russian president but put him safely in a box?

Anything – anything – that could usher in a temporary ceasefire should be considered, for the sake of all those Ukrainians (and indeed Russian soldiers) who will other-wise die. But such a ceasefire would only be a prelude to serious negotiations. We’ll be outsiders, but the West will have considerable power to influence Ukraine. I’d argue that there are some things the Ukrainians can be encouraged to put on the table. Their eastern breakaway statelets are not coming back and anyway would be more trouble than they’re worth. Crimea is not coming back. Perhaps an undertaking not to seek membership of Nato might be thrown into the mix. But that’s about it. Ukrainian aspirations to become more like free European democracies should not – cannot – be crushed. Longer term, that may mean being allowed to join the EU, and this dream should surely not be bargained away.

I cannot see in the offing the outline of a deal Putin could accept. If he did, it would be seen as a serious reverse and perhaps the end of his presidency. Russia would know that pursuant to such a deal the western allies would do all in their power to arm, protect and encourage Ukraine, bringing the country further into the free European fold. Negotiations to establish a permanent new status and future for postwar Ukraine would probably be existential for Putin’s presidency. Nevertheless, if there is a chance, we should try.

If negotiations fail, what then? The war continues, Russia finally grinds her bloody way to some kind of victory, and years, maybe decades, of a terrorist-style Ukrainian insurgency follow. In such a case, all the sanctions imposed on Moscow must surely stay, with perhaps more added.

But what if Putin is overthrown in a palace coup? Does the West hold out an implicit promise that sanctions gradually be withdrawn? Or do we suppose that Putin’s successors will be as dangerous and unreliable as him, and that it is the personality of the Russian state rather than of one individual that is the problem?

I’m inclined to the latter. This war has awoken us to the true nature of a vast and dangerous nation. Perhaps we may gradually come to re-establish a certain level of business and financial dealings, but I can’t escape the conclusion that a version of Cold War containment is the only way. We are now surely alive – as before we were not – to the danger of relying on Russia for our energy supplies. Whatever happens in Ukraine, we must urgently continue that uncoupling. We British have also been alerted to the presence among us of many kleptocrats. We shall surely not wish to recover our status as a jurisdiction where robbers hide their winnings.

We have learned, too, the importance of defence. Even if the status of Ukraine is settled in that country’s favour, nobody will forget what Russia tried to do, or how military advance must often be countered by military resistance. Increased defence spending should be a permanent consequence of what has happened.

And on another, higher, level, I think we have learned that bad countries with expansionist ambitions have to be confronted, that the free world has to cooperate in resisting them, and that early and firm resistance is often better than waiting until the writing is on the wall. After Russia, I think we will be looking at China more warily, with an enhanced willingness to act. I repeat what I suggested on these pages many weeks ago. Absent – which in a way no humane person wholly can – the wretched outcome for many Ukrainians, there is a sense in which this ghastly episode may prove good for the free world.