When Bob Obuchowski was 11, the Nazis came into his small Polish town of Ozorkow. The 2,300 Jews were forced into a school building and made to undress, then lined up and stamped either A or B to indicate their destination. Most, including his parents and all but one of his three siblings, were sent straight to their death. The 500 who remained were incarcerated in a ghetto.

"Everything was like a joke until we saw the way they were selecting people and taking the babies away from their mothers," he recalled. "It didn't matter how old you were. We realised that the Nazis meant business."

Mr Obuchowski spent three-and-a-half years in the Lodz ghetto, where disease and starvation were rampant. "What we'd get for eight days was enough for maybe two." Such was the hunger that, if someone died, people would hide the body for days on end in the hope of obtaining extra rations.

He was severely scarred from illness and, when sent to Auschwitz in January 1945, he knew that if the guards noticed this, he would be shot. Fortunately, they looked away as he walked past during selection.

From there, Mr Obuchowski was sent on death marches to Buchenwald and then to Theresienstadt in Czechoslovakia.

"We walked and slept in the snow," he said. "We had no underwear or socks and hardly any food. It was hell."

He was one of 75 survivors out of the 2,775 who started the march to Theresienstadt and was close to death from typhoid when the camp was liberated. Post-war, he was one of the first survivors to arrive at Windermere in the Lake District, where he recuperated. Now a great-grandfather, he lives in Redbridge.

Mr Obuchowski regularly gives his testimony to pupils across the country as a speaker in the Holocaust Educational Trust's Lessons from Auschwitz project.