Chief Rabbi Ephraim Mirvis has called for community members to be "a new generation of heroes", prepared to take up the educational baton from Holocaust survivors.
In an emotional address to more than 3,000 people at the national Yom HaShoah commemoration at Barnet Copthall Stadium in north London on Sunday, Rabbi Mirvis said that "throughout our schools, our cheders, our synagogues, there are shadows. There were more than one million children among the dead who never lived to raise families. And for the vast majority, there is no one to say Kaddish for them."
Although Holocaust survivors were "a remarkable resource for our society, they will not live forever.
"We are the ones who must come forward and spread the message so the Shoah may never be forgotten. We owe it to the six million, to our brave survivors and to the children who perished in the Shoah - the shadows who will never leave us."
Echoing the sentiments, Israeli Ambassador Mark Regev said that "preserving the memory of the Holocaust is more important today than ever before".
Speaking "not just as an ambassador but also as the son of a survivor", he reflected that "many hoped that antisemitism would contract, and ultimately disappear, after the Holocaust.
"Sadly, that has not happened. Today Jews are still being vilified and targeted just for being Jews, in the Middle East and in the heart of the West. Israel is being targeted with the same slurs that have been thrown at Jews for time immemorial.
"Friends, this crazy obsession with the Jewish people and their state has a name - it's called antisemitism. But we are no longer a stateless people searching for a safe haven, no longer powerless. We are sovereign."
Survivor Ben Helfgott told the crowd that the day "evoked painful memories" for him. But the Holocaust must continue to be spoken about because "evil is ever present.
"Our generation of survivors cannot last forever. But the lessons will, because you will remember and keep teaching them."
Guests at the ceremony included Sadiq Khan, on his first official engagement as London Mayor.