However, it was not until 1989 that the Green Party made an impact in national politics, winning its first seat in Dáil Éireann through Roger Garland.

[citation needed] At a meeting of the council, he waved a cheque he had received in the post from a builder who was seeking to rezone land for a housing development.

Sargent alleged that Fianna Fáil Councillor Don Lydon put him in a headlock and attempted to snatch the cheque from him.

[3] This is one of the incidents which eventually led to the creation of the Mahon Tribunal to look into planning matters in Dublin County Council.

[4] Having been elected to the Dáil, he resigned his county council seat in keeping with Green Party policy on dual mandates.

At a special Leadership Convention in Kilkenny on 6 October 2001, Sargent was elected the first official leader of the Green Party.

[9][10][11] On 23 February 2010, he resigned as a Minister of State when he admitted unlawfully contacting Gardaí about a criminal case involving a constituent who had been assaulted.

In 1987 he helped found Sonairte, The National Ecology Centre, in Laytown, County Meath and served as chairman.

Sargent lived with his second wife, Aine Neville, in Tacumshin, County Wexford, where they developed an organic horticulture enterprise.