Heidenfeld was born in Berlin. He was forced to move from Germany to South Africa because he was a Jew. There, he was South African chess champion eight times, and he represented South Africa in the Chess Olympiad in 1958. Besides chess-playing he was also a writer, door to door salesman, journalist and designer of crossword puzzles. His hobbies were playing poker and collecting stamps as well as playing chess. During the war he helped decode German messages for the Allies.
In 1955 he beat former world champion Max Euwe. He also won games against Miguel Najdorf, Durao and Ludek Pachman. He never became an International Master - he did eventually attain the required qualifications but declined to accept the award from FIDE.
He wrote several chess books including Chess Springbok, My Book of Fun and Games, Grosse Remispartien (in German) and Lacking the Master Touch (1970).
In 1957, after visiting Ireland, he moved to Dublin. In 1979 the family moved back to Ulm where he died two years later.
He was Irish Champion in 1958, 1963, 1964, 1967, 1968 and 1972
He was in the Olympiad team in 1966, 1968, 1970 and 1974; and in the European Championships team in 1967.
His son Mark Heidenfeld also played chess for Ireland.