Oltmans was a journalist. He got on the bad side of the Dutch government after interviewing Sukarno, the Indonesian president in 1956. The Government then did all kinds of things to make it difficult to work, and in 2000 he received ƒ 8,000,000 in damages. He also kept a diary and he published memoirs. He donated all his papers to the Koninklijke Bibliotheek (Royal Library). This year the last part of his memoirs were published.