Dealing with Russia has never been simple. In geographical size it is immense. In political culture it is secretive and as tough as nails. “Containment” was the order of the day when Soviet communism held sway. Then the west, seized with the fanciful notion that post-Soviet Russia would blossom into a free-market democracy, with a middle class wedded to peace, property and the rule of law, made an effort to build a “strategic partnership” with Moscow.

That effort lies at the bottom of the Black Sea, sunk by Russia’s annexation of Crimea in March 2014, its military intervention in eastern Ukraine and poorly conceived and executed western policies in the post-Soviet neighbourhood. Now an older theory is back in fashion, which depicts an unbridgeable gap between Russian and western values. It asserts that this gap, though widening under Mr Putin, must in its deepest sense be understood as a reflection of profoundly different historical experiences in modern Russia and the west. On the Russian side, it has stimulated a censorious, anti-western conservatism on social questions. It has sharpened a propensity to use military force against neighbours, notably Georgia and Ukraine. It is suffused with truculence towards Nato states. As a result, the west must be on its guard.

This theory has strengths and weaknesses. It rightly emphasises the importance of domestic factors in the way that Russia formulates and conducts its foreign policy. On the other hand, it risks falling into the conceptual error of confusing an authoritarian strongman with an entire society, as if the wills of Mr Putin and 140m-plus Russians are one and the same.