As a former president of the Irish Farmers' Association, Mr Gillis was able to count on support from well beyond Fine Gael's core vote when he succeeded in winning a European Parliament seat in 1994.
His standing with the farming community will continue to be of benefit. An active member of the Church of Ireland, he lives in Grangecon, Co Wicklow, and is married with five grown-up children.
An engineer by profession, he is a "farmer by choice of career", having started in the 1960s by purchasing a small farm in Kill, Co Kildare. He later purchased the 375-acre farm where he now lives.
Aged 63, he is among the very few MEPs to have spent time in prison for his activities, as a result of his involvement in the farmers' rights struggle of 1966.
He has maintained his interest in agriculture in the European Parliament where he is a member of both the agriculture and BSE inquiry committees. He is also vice-chairman of the Afro-Caribbean Pacific committee and a member of the development committee.
He led the IFA through a difficult period in the early 1990s, healing the wounds left by the resignation of his predecessor, Tom Clinton, while dealing with the MacSharry reform of the Common Agricultural Policy.