It was a chilly morning in Afghanistan last Saturday when I walked among the gravestones and sensed the eerie pathos of the British cemetery in Kabul. And I reflected that here in 1842, General William Elphinstone was driven from his cantonment with a few thousand soldiers and their great rabble of camp-followers.

As they marched through the passes east of Kabul, Elphinstone’s army was ambushed and cut down almost to a man.

Of Britain’s 19th-century presence in Afghanistan, there is no legacy save this cemetery, desecrated by the Taliban and reduced to decrepitude by years of civil war. Then — almost incredibly — in the 21st century the British returned and carefully repaired the cemetery, adding the names of the 456 servicemen and women who have given their lives in Afghanistan in the past 15 years.

This time, they came not for imperial glory but in the hope of improving the lives of the Afghan people and ensuring the safety of our own country. And I asked myself, what manner of people are we — the British — that we keep sending our soldiers thousands of miles from home? What drives our instinctive globalism, the wanderlust of our traders, aid workers, journalists and entrepreneurs — and of the diplomats whom I am now privileged to lead?

Some people have been driven to ask this question by our decision to leave the European Union. Some have even chosen to interpret that vote as evidence of Britain abandoning the spirit of former years and choosing to turn inwards. I emphatically reject this view. Rather than hauling up the drawbridge, Britain is a nation on its mettle, refusing to be defined by Brexit and galvanised by the new possibilities ahead.

We are what we have been for centuries: a country that is politically, economically and morally fated to be outward-looking and engaged with the world. That is what I mean when I speak of Global Britain. And everything I have seen as Foreign Secretary has only reinforced my conviction that this global outlook is profoundly beneficial both to Britain and the world.

Why? First, because it is in our national interest to contribute to global peace and order, building the security to invest that is the bedrock of economic growth. And the world today is more dangerous than for several decades. We have the cult of the strongman. We have an arc of instability across the Middle East from Iraq to Syria to Libya. Britain’s answer will never be to cower and put our collective heads under the pillow.

Redoubling resolve

We know that faraway events can affect our lives, too. After the Second World War, Britain and America sought to create a new international system based not solely on power but on rules embodied by global institutions. Alongside our American and European allies, we were present at the creation of the United Nations and Nato. When the Cold War ended, we hoped that our rules-based order would spread and embrace the world.

Alas, that vision has not really come to pass. Instead, the great attempt at a liberal settlement is now under unprecedented challenge. Some countries only observe the rules that serve their interests; terrorist movements such as Daesh (the self-proclaimed Islamic State of Iraq and the Levant) regard the very concept of a liberal order with contempt. And it is precisely because of these challenges that we in Britain must redouble our resolve to defend the best of the rules-based system.

In this supreme task, we will always work alongside our European friends. Next year, British troops will deploy in Estonia to deter Russia and demonstrate our resolve to keep our Nato obligations.

At the heart of Nato lies the security guarantee in Article V of the North Atlantic Treaty, declaring that an attack on one ally “shall be considered an attack against them all”.

In offering that guarantee, President-elect Donald Trump has a point. It cannot be right that one Nato member — America — accounts for about 70 per cent of the alliance’s defence spending. I want every Nato ally to follow Britain’s example and meet the agreed target of investing 2 per cent of national income on defence.

Back in that post-war moment, it was John Maynard Keynes who helped create the Bretton Woods institutions that allowed a dramatic growth in world trade, lifting billions out of poverty. And yet support for free trade is ebbing away; for the first time in decades, trade volumes are no longer growing as fast as the world economy.

One of Britain’s historic tasks after Brexit will be to campaign for free trade. In doing all this, we will be fortified by the appeal of our values. And we must always recognise the limits of what we can achieve.

When I met President Ashraf Gani in Afghanistan last week, he thanked me for the sacrifice of British troops and he was categorical that, this time, our legacy was positive and lasting. I have been repeatedly impressed by how people around the world are looking for a lead from Britain, engagement from Britain. In standing up for a liberal international order, I believe that this country is overwhelmingly a force for good, with the power to do even more. And we should not be nervous of saying so.

— The Telegraph Group Limited, London 2016

Boris Johnson is British Foreign Secretary.