Gordon Brown: Madiba taught us how to live – and act – in hope

For many of us born in the second half of the 20th century, the anti-apartheid struggle was the defining political question of our time.

It is hard to conjure now just how the blood ran cold when we saw pictures of 12-year-old Hector Pieterson dying in the arms of another student during the Soweto Uprising; or how we felt when we read that Steve Biko had died in police custody. These were not simply news reports for us – they were messages from our extended family, reports of friends we may have never met, but whose fate was bound with ours.

This oppression in South Africa did not simply define how one felt about the tyranny of racism, but summoned us to answer how we felt about hope itself. Because the anti-apartheid movement asked us not simply for our outrage – but for our solidarity. It called us not to live in hope but to act in hope – to believe that no injustice will last forever if people of good conscience are prepared to stand up and speak out.

I remember there were those who opposed sanctions or even wore "hang Mandela T-shirts", but the majority of British people can be very proud of their role the struggle, whether through boycotting South African products, supporting sanctions, protesting in Trafalgar Square, joining the concert protests or in thousands of different ways adding their voices to the cries of those in townships and jails a continent away.

My first frontline involvement in the anti-apartheid campaign was as editor of our campus newspaper almost 40 years ago at Edinburgh University. Through a painstaking investigation we exposed the University's shares in apartheid South Africa, and eventually forced their sale. So many of us could tell similar stories – of the rugby matches boycotted, the holidays not taken, the petitions signed.

The contribution of the British people – the trades unions, the student movement, the Liberal and Labour Parties, the ordinary shoppers who did their bit – all of it should never be forgotten.

It was this story I carried with me when I met Nelson Mandela – Madiba – for the first time. He turned to me with a smile, and pointed: "Ah, representative of the British Empire!" It was typical of the man; forgiving, playful, utterly gracious and with a generosity of spirit that lifts the world.

One day we will explain to our children why so many streets, student union buildings, council chambers, town squares and children in Britain are named after this man from so far away. We will tell them about a great uprising of hope – a time when the British people stood up for justice, and we prevailed.

And so the lesson of the South African struggle is surely that change never comes without a fight, but when we fight, progressives can change the course of history. That is exactly the lesson we should heed as we tackle the great global causes of today; poverty, climate change, terrorism, nuclear proliferation. Thirty years ago today nobody would ever have believed that apartheid would crumble, but 20 years ago today Nelson Mandela walked into the sunlight a free man. The story of the campaign for his release – like that of Aung San Suu Kyi who remains oppressed today – is that while the road to justice is long, nobody need ever walk it alone.

Change comes to those with the courage to will it; 20 years from now let people say this generation created a decade not of austerity, but shared prosperity, not of conflict, not of peace, not of inequality and climate chaos, but of sustainable development in the interests of all.

The anti-apartheid struggle shows what can be done when people come together to build a better world; there is nothing to do now, but begin.