"They weren't really people, they were semi-corpses," said former soldier Bernard Levy describing the scenes that greeted British troops on entering Bergen-Belsen in April 1945.

He was speaking to a group of over 200 students and teachers brought to the site of the concentration camp on Sunday by Holocaust Educational Trust to mark the 70th anniversary of its liberation.

The 11th Armoured Division of the British Army entered the camp in northern Germany on April 15 1945. Around 70,000 inmates had died there from disease and starvation.

The HET delegation joined the Association of Jewish Ex-Servicemen and Women for a commemoration ceremony.

The Shabbaton Choir sang the shema and Chief Rabbi Mirvis addressed the group, saying: “No words can sum up our deep sense of grief and anguish and sorrow, and no words can adequately do justice to their memory.

“Because Bergen-Belsen was razed to the ground it is left up to the imagination, for us to presume what took place here. We imagine the unimaginable. How do we describe the indescribable?”

The camp buildings were burned to the ground by British troops after the liberation to stem the spread of disease. All that remains are memorials and the raised mounds of mass graves, marked by headstones stating the body count. One of the largest reads “2500 dead”.

Ajex member Mervyn Kersh was stationed in the nearby town of Celle during the liberation. He recalled his shock at seeing the inmates.

"I saw people who could walk walking in their camp uniforms to Hanover station. It was a long way to walk but they did. They looked very scraggly but obviously they were the stronger ones."

The HET and Ajex delegations were taking part in an international commemoration attended by Joachim Gauck, the German president, and the Duke of Gloucester.

HET participants from all over the country flew into Hanover for the day to visit the former camp site, and attend a second ceremony at the Jewish cemetery at the Bergen-Hohne Garrison of the British Army which was used as a displaced persons camp for inmates after the liberation.

Thousands died at Bergen-Hohne from malnutrition and disease in the months following the liberation.

British soldiers stationed at the barracks joined in the intimate commemoration where kaddish and psalms were recited.

After the ceremony HET invited the group to lay a stone on the Jewish memorial, explaining the act's significance in Jewish tradition.

HET chief executive Karen Pollock said: "I feel really proud that we could bring 200 young people and teachers across Britain to Belsen.

"They feel privileged to be asked to come."