Having been nursed back to health he returned to Hungary, hoping that someone else from his family might have survived the Holocaust. However, out of an extended family of 57 people, he was the sole survivor. He restarted the family business, but it was nationalised in 1949 by the Communist regime. He then escaped from Hungary, became a refugee in Austria and was accepted as a migrant to Australia, where he worked first in the world-renowned Snowy Mountains Hydro-Electric scheme, and later at the Australian Atomic Energy Commission. He married and made a family in Australia, moving to England with his wife and three children in the early 1960s. He worked at the British Library in Yorkshire, then a few more years at Leeds Metropolitan University.

Parallel with his working life, and long into retirement, John was heavily involved in voluntary work with disability issues, nationally and internationally. For many years he served not only on the national council of Mencap, but also on a similar world governing body on intellectual handicap. In recent years he have gave many talks about his Holocaust experiences in schools, at The Holocaust Centre and in Germany, in the hope that younger generations could learn from those events and work for a better future.