[2] He left Spotswood College at age sixteen to become an electrician, and eventually became a technical teacher at the collegiate and polytechnic level.

Duynhoven entered Parliament in the 1987 election, winning the New Plymouth seat from incumbent National Party MP, Tony Friedlander.

[4] In 2003, Duynhoven raised with the Speaker of Parliament his status, and whether he might have breached electoral law, thus disqualifying him from retaining his seat.

His father was from the Netherlands, and Duynhoven had possessed citizenship from birth, but had temporarily lost it due to a change of Dutch law.

The Speaker ruled on 23 July 2003 that Parliament's Privileges Committee, who were until 2002 responsible for determining whether a vacancy exists, would consider the matter, and that he would be guided by their report.

The Solicitor General advised the Privileges Committee that the law was clear, and that Duynhoven's seat became vacant on 11 June 2003.