Originally intent on a career with the diplomatic corps of the foreign service, he ended up working in press offices in the Netherlands (1953–1955).

Having paid two million guilders in lawyer's fees, Oltmans bought a penthouse on a canal in Amsterdam and a Steinway piano.

Oltmans was based in the US in the 1960s, where he worked as a reporter for Dutch TV broadcaster NOS and lobbied members of the President Kennedy's administration regarding New Guinea.

[9] Joseph Luns, who was a prominent Dutch diplomat, vehemently opposed this transfer and subsequently had Oltmans declared persona non grata for life.

[12][13] In 1977, De Mohrenschildt agreed to disclose information to Oltmans, but disappeared from their meeting place and was found dead in Florida a few weeks later.

[15] On 29 March 1977, De Mohrenschildt was found dead at his daughters home in Florida due to an apparent self-inflicted shotgun wound via the mouth.

[16] A few days later, Oltmans told the HSCA that de Mohrenschildt had implicated himself in the conspiracy to kill President Kennedy.

Looking for a more poised perspective on the one sided bad image of the evil empire's communist power, he often traveled to Russia.

Together with the Kremlin's foreign expert Georgi Arbatov, he wrote the book 'The Soviet position', elaborating on Moscow's perspective on the east–west issues in 1981.

[1] Due to the ban imposed on him by Minister Luns, Oltmans was forced to help support himself through his family's inheritance; the death of his parents (1966 and 1974) and some bad investments caused him financial difficulty.

In the late eighties, he intended to use his large global network as a consultant to introduce entrepreneurs to Eastern European business opportunities.

His investigative reporting was not appreciated by the shaky South African regime of the time and in August 1992, he was deported to Jordan on charges of espionage.