At the very close of his frontline political career, in 1955, Sir Winston Churchill had two final pieces of wisdom for his cabinet colleagues as he approached the end of a second term as Prime Minister. The first was psychological and ennobling: ‘Man is Spirit’. And the second was practical: ‘Never be separated from the Americans’.

Both were good advice, and the latter is especially so, as we consider the world of the twenty-first century: a world of constant competition, the threats of open wars of conquest by revisionist powers, and the increasingly fundamental challenge posed by authoritarian states to global democracy and the concept of an open society.

Britain and America demonstrate the greatest alliance in the history of the world: an alliance which has done more to preserve democracy than any other in history. In a new era of defiance of democracy, Britain’s remaining close to the Americans has never seemed more vital.

In Churchill’s speech in Fulton, Missouri, in 1946, he spoke of his ‘full liberty to give my true and faithful counsel in these anxious and baffling times’.

Observers of the international scene making use of a similar privilege note the resonance. Just as Churchill’s speech announced the Cold War and defined the Iron Curtain, we must concede that Russia’s invasion of Ukraine has changed the world. Indeed, it has made the world more anxious and more baffling.

This is a time of challenge. The Communist dictatorship in China is increasingly totalitarian. As is the regime of Vladimir Putin in Russia. The two are close allies: they coordinate, with a network of other authoritarian states, to take over or to derange global institutions like the United Nations, its Security Council, and the World Health Organisation.

Unless this trend is challenged, it risks undermining those international bodies which have stood for accountability and responsible global management, and the licensing in the confusion of aggression, chaos and war – and all their accompanying evils.

As Churchill said at Fulton of the United Nations, “We must make sure that its work is fruitful, that it is a reality and not a sham, that it is a force for action, and not merely a frothing of words”. After years of drift, in the last year, this is something Britain and the United States have begun successfully to do.

Britain and America successfully warned an unwilling world of the reality of Russia’s invasion of Ukraine: using the very international institutions which Russia had sought to pervert as pulpits to propagate the truth.

As Chinese diplomats attempt to undermine global financial institutions like the World Bank and IMF with its Belt and Road Initiative – in order to create a world of client and tribute-paying states – Britain and America are well-placed to prove that free economies create prosperity better than debt traps.

And as Russia’s war throws away the lives of a whole Russian generation, British and American diplomatic efforts prove that the open release of intelligence can make public what tyrannies would rather conceal – be that evidence of massive corruption, or the aggressive wars tyrants launch without the consent of their people.

But more must be done. The democratic world at large has only lately woken up to the threats posed by networked authoritarians intent on geopolitical revisionism.

Only by cooperating can the democracies ensure that their voices are heard in international bodies and world bureaucracies. Only by using together the vast economic strength of the free nations can the threat of sanctions deter countries like China from following Russia’s folly in launching an unprovoked war of aggression.

Our age is, as Churchill said of his own time, a moment of anxiety.

The Special Relationship must be at the heart of this new resurgence: an undying friendship united in common goals of political freedom and the rule of law – the linchpin of a wider Western Alliance.

It is a friendship forged by diplomacy, tested on the battlefield and the bitter seas of the cold Atlantic: a friendship of close security cooperation and integration.

Our age is, as Churchill said of his own time, a moment of anxiety. It is still uncertain whether international institutions will survive the authoritarian assault. If the norms of peace and diplomacy will hold.

Only if Britain and America are together and united can we confront the security challenges of this century. This era could, if the two countries are disunited, produce a ‘quivering, precarious balance of power to offer its temptation to ambition or adventure’ – but together, another path is possible.

Only if the two stand together will there be, as Churchill said, “an overwhelming assurance of security” – a security a century in the making, still unfinished, but one undergirded by the shared sacrifice and affinity to two great English-speaking democracies as Britain and the United States. Let the two never be separated.