The Prince of Wales has described the Holocaust as "not just a Jewish tragedy, but a warning to all of us".
Addressing survivors and leading political and religious figures at the UK's national Holocaust Memorial Day ceremony at Central Hall, Westminster, on Tuesday, the prince said the Shoah was "an unparalleled tragedy and an act of evil unique in history.
"It is for these reasons that we must always remember it and honour its Jewish victims and the Nazis' other victims.
"The memory of this subject, and the unspeakable yet almost incredible details of the Nazis' diabolical plan, can help future generations to understand not just what happened across Europe, but how it came to happen and why similar terrible things have happened in places such as Bosnia and Rwanda.
"It should also help us to reflect on how we should respond to events in the Middle East today.
We will not allow any excuses for antisemitism in our country
"We so often fail to stop these tragedies in time because the circumstances are always different, but this only makes Holocaust Memorial Day more important than ever.
"I could have read from the writings of Anne Frank, or her like, who wrote so tragically about their experiences.
"But what I find so moving is the three lines scratched in the wall at a concentration camp: 'I believe in the sun even when it's not shining. I believe in love even when I don't feel it. I believe in God even when he is silent.'"
David Cameron praised the many "incredible" survivors who went into schools to share their testimony, "reliving the most harrowing moments of humanity so we may never forget. For years, survivors have seen this as their duty to us.
"It is time for Britain as a nation to stand together and take on our duty to them. To say, 'we will remember them, we will not allow any excuses for antisemitism in our country, not let anything destroy the multi-faith, multicultural society that we have built'.
"And we will make sure that they can learn from the stories of our Holocaust survivors before they are gone."
Chief Rabbi Ephraim Mirvis also stressed the importance of Holocaust education, "so we can all recall the horrors of the past and create a destiny of peace for our future".
Among the 200 survivors at the ceremony was Austrian-born Freddie Knoller, 93, who endured the death march from Auschwitz to Loslau. Speaking beforehand, he said he had found happiness in the UK.
"I love living here. We have two daughters and one grandson and it's wonderful. I'm still the eternal optimist and I recommend that everybody who has a problem should be more optimistic. I'm very happy. I'm a lucky guy."
The ceremony was presented by actor Adrian Lester and featured readings from Sir John Hurt, Michael Palin, Christopher Eccleston and Natasha Kaplinsky.
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