It has taken six months and the deaths of thousands of Ukrainians but now, at last, Donald Trump may have grasped the truth about Vladimir Putin.

As he threatens new sanctions and denounces Putin as “crazy”, the president is finally working out that Russia’s leader is implacably determined to conquer Ukraine and rebuild an empire, at whatever cost in blood.

But Trump is not alone in having lessons to learn: so, in all honesty, does the Foreign Office.

Ever since Putin launched his full-scale invasion in February 2022, our diplomats have been at the forefront of backing Ukraine and maximising the pressure on Russia.

They saw the onslaught coming and their response has won immense goodwill for Britain among Ukraine’s government and people.

On Friday, the Foreign Office named and sanctioned 18 Russian spies accused of covert bombings or acts of sabotage in Britain and elsewhere, designed to prevent support for Ukraine.

Yet before 2022, the truth is that British diplomacy was not always so clear and resolute about countering Putin’s aggression.

Now that we are re-engaging with China – by far the most powerful of our adversaries – it has never been more urgent to understand the dangers of dealing with hostile states.