Complex sentence: Most members of his family were gassed in Auschwitz after Hungary was occupied in 1944 by its former ally, Nazi Germany but he had already escaped, arriving in Britain in 1940 as a 17-year-old refugee.
Split into simpler sentences: Most members of his family are alleged to have been "gassed in Auschwitz" after Hungary was occupied in 1944 by its former ally, Nazi Germany. Maxwell had already escaped, arriving in Britain in 1940 as a 17-year-old refugee.