Much of what we’ve seen and heard today was inspired by an extraordinary act of defiance and hope, by a small group of people in the Warsaw Ghetto.

Picture them in your mind. They have been herded together in an enclosed space as if they were cattle, not human beings. They have seen 100,000 of their number die of starvation and disease, 270,000 taken in cattle trucks to Treblinka and other camps to be gassed, burned and turned to ash.

And all this is happening not in some remote place far from public eyes, but in the middle of Warsaw, capital of Poland, one of the centres of European civilization. How they kept sane, how they kept going, summoning the will to live, is beyond me.

But it was there, in the midst of the unchecked rule of evil, that they conceived a plan: to record every detail of what was going on around them, so that future generations might know.

This group of people, gathered around a young historian Emanuel Ringelblum, sat down to write history as it was happening, because they knew, with a chill as deep as death, that not only were they witnessing the single greatest crime in the history of humanity; they also knew that the perpetrators of that crime were planning to obliterate every trace of the crime itself.

Thousands kept diaries and wrote testimonies, each a witness to an evil we still find hard to understand.

What moved them? Remember: they knew that maybe none of them would survive. They knew that the Nazis would search for and destroy any evidence of the great destruction. They knew they had to hide what they had written so well that there was a real possibility that it would never be found.

What they had was nothing less than faith. Faith that the documents would one day be discovered. Faith that those who found them would understand what they were and why they had been written.

Faith that evil would not win a final victory. They had faith in humanity when almost everyone had betrayed them. They had faith in us. And we must honour that faith.

Among those who most honoured it were the survivors. I have known many Holocaust survivors. And what has struck me time and again is how they have fought for the future instead of being held captive by the traumas of the past. They have contributed to Britain, its arts and sciences and businesses and academic life.

They or their children have helped survivors of other tragedies. In Rwanda, children of holocaust survivors have built a youth village for orphans of that great massacre.

Fighting the pain of ancient wounds they’ve told their stories to schoolchildren, teaching them what freedom means and how it must be fought for in every generation.

They’ve taught us that by acting together we can defeat the evil that lies dormant but not dead in every human heart. They’ve taught us that only by recognising our shared humanity do we become fully human.

They have left us a legacy of hope and we must never let that legacy die.